You results are very similar to what I've experineced here in my garden.
I've tried two different supposedly Mortgage Lifter's. The last one was the Estler's strain. It was like yours. Huge and without checking records I believe no fruit set. Maybe one. Know I marked it off. That was two years ago in a year where most did well especially late. My impression was it didn't like something about our climate. And there are many that way. Along with most of the Brandywines and several others I could name.

Cherokee Purple is a lot like Kellogg's Breakfast in that they seem to be a little slower but it has always produced well here if you have the true one and not the false one floating around. It did well in a terrible year last year. Seems to hang in and just keep producing more. Have never had much disease problems with it also. Knock on wood.
Jay

Sure some others will let up know how ML has done for them. My climate is a little different than most of OK. So my experience may not be typical. Although I've read of others having low production from it. Then there are those who get great production. Like any variety. You have to find what does well in your garden. Jay

Arizona Sooner,

It is odd how tomatoes perform differently from location to location, and I have better results from some varieties some years than others. So much is dependent on the weather when you're growing tomatoes.

I have grown both Radiator Charlie's Mortgage Lifter and Estler's Mortgage Lifter and most years they have performed very well for me, although Estler's has produced more fruit early on and Radiator Charlie's produced a decent yield, but fairly late. And, I should clarify that by saying that the Radiator Charlie fruit were fairly late to ripen----I consider it a late-season tomato here, usually ripening no earlier than mid-July to early August for me here in extreme southcentral Oklahoma. In order to have ripe fruit in July, it did bloom/set fruit in the May-June time frame, and maybe even in April in those years when I set it out in mid- to late-March and didn't have a late freeze set it back. It just takes RC forever to ripen.

Estler's ML was much earlier and much more productive and I think I'll probably put it back in my growing rotation for next year.

Sungold and Sioux have done well for me although Sioux is later than many of the other varieties I have in my garden. I grow SunGold every year and it produces all summer long here in very hot and dry conditions. I have Mountain Fresh Plus started for the fall, and Creole had serious disease issues the two years I grew it so I didn't give it a third chance here.

Cherokee Purple and Black Krim have been two of our favorite tomatoes ever since the first year I grew them, so for at least a decade now I guess, but have been bumped out of the growing roation by Indian Stripe and True Black Brandywine, both of which produce earlier and heavier yields and both of whom produce better in the extreme summer heat. Indian Stripe is believed to be closely related to Cherokee Purple and it is incredibly similar, but better in flavor, quality and production as grown here in my garden.

My climate is significantly different from Jay's (his is significantly drier than mine almost every year) and so is my soil (he has sandier soil and I have clay) and that probably accounts for the different results. Plus, most years (knock on wood) I am able to plant a month or so earlier than he can in his colder zone.

With tomatoes, too, timing is everything. I always get the best fruit set from plants set out in mid-March through mid-April. Anything that goes in the ground later than that doesn't produce as early or as well. Remember though that I am as far south as you can go in Oklahoma and still be on the right side of the Red River. Were I any further south or west, I'd be in Texas, so I'm in zone 7 and can plant somewhat earlier than y'all can in zone 6.

If it were my Mortgage Lifter, I'd be patient and wait for fruit set. Often, it is just when you are giving up on a plant that it finally kicks in and starts blooming heavily/setting fruit. You can encourage the fruit set by thumping the individual blossoms or by giving the plants a firm shake. I have found this works best for me if I do it in the very early morning hours before it gets too hot. I have better luck with shaking, too, than with thumping. The flavor and texture of Mortgage Lifter are outstanding and it is worth waiting for.

I am a little concerned about this week's temperatures. Here where I live we're going to be in the upper 90s, but even if temperatures this week inhibit pollination, cooler weather that is expected this weekend will give our tomato plants a chance to pollinate. Other ways you can encourage fruit set in this heat is to lightly mist your plants--especially the flowers in the early morning to cool them down, and even partially shade them with shade cloth during the worst of the summer heat.

Be sure the ML is not getting a fertilizer that is high in nitrogen. More than many other varieties, I've noticed ML tends to go nuts on foliage production if it is fed nitrogen and it probably does that at the expense of the flowers.

If you feel like all of your tomato plants are really underperforming, you can try to give them a quick boost with a fertilizer that is meant to encourage flowering. A lot of the folks who grow giant tomatoes for competition give their plants a bloom booster fertilizer early in the growing season to encourage flowering. I don't know if a bloom booster would help tomatoes this late in the growing season and with serious heat already here it might not help, but it probably couldn't hurt them either.

Dawn

Dawn hit on a few things I think are important. One is soil type. Here in my deep sany soil I have no problem with water retention. And water can change how a tomato tastes. One that comes to mind is one of my favorites Kellogg's Breakfast. Last year I was discussing in emails with another grower how much I liked it and he was stating he never found the flavor I did. His soil is tighter and he also gets more moisture. We decided it might be the moisture. So he didn't water it like the rest and when it didn't rain it moved way up his list. He said when it rained the flavor declined. I also noticed the flavor of it is influenced by temperature more than most.
Although we've had severe trying conditions the last two years I have some difference in conditions which change the results for me in an average year. Although we get high temps we have lows in th e60's most nights and on most days we have low humidity. Which allows us some fruit set even in 90 degree plus temps. The thing that has hurt us the last few years in the higher than average winds.
Some tomatoes seem to do well in this climate and others struggle every year I try them. I got one called Kanora from the USDA seed bank. It was developed in the 20's and stabilized by Kansas State University. It did well here last year and so far this year has good fruit set. Black from Tula is another that sets well here most years. Another steady performer is Glick's 18 Mennonite. It has several on it now. And so far here Cherokee Purple has out performed Indian Stripe. I know Dawn has had opposite results. It is ahead again this year. The PL versions are also setting fruit. I agree with thumping and shaking the plants. I usually shake the cages and use a soft bristle broom on my sprawlers. I just walk by and give them a good sweep. I got started a little late this year.
Another thing with me is most of my plants will make it through the whole season. I don't plant a 2nd crop per se. I just plant from April into June. The later ones usually are my best producers after Sept 1st. Jay

I've grown a couple strains of Mortgage Lifter and have both crossed off of my list. Production wasn't zero but I was surely underwhelmed enough to not bother growing it again.

Cherokee Purple did pretty good for me and I absolutely adore Creole and Sioux. I've not grown the others you mention.

I'm in LeFlore County, by the way, down in the SE corner of the state.

Thanks for all of your input!

I am out of town on business, so I asked my wife to go out and give the ML tomato plant a good shake but she said that it probably got a good shake the other night when we had a mini-heat burst downdraft out of a collapsing thunderstorm. She said that same gust of wind knocked over the Sungold, but I am not concerned as that plant can sprawl anywhere and still do quite well. I'll pick it up when I get home on Friday....