If you are going to need to net cherries from birds you should remove lowest branches to help make spot to tighten netting around the trunk at the base.

I train trees at first to a central leader and remove all branches on cherry trees more than half the diameter of the trunk at point of attachment to the trunk. You don't have to do this if you want a low open center tree- but remove branches so over sized that they have inverted bark which makes them weak and likely to break.

Sour cherries don't require much technical pruning- they aren't pruned to improve size and quality of fruit much.

There is no hurry to cut out the center and you can wait or cut it out now if you are happy with the placement of existing scaffolds.

Your trees will establish much more quickly if you eliminate the competing grass. Keep mulched 5' diameter circles at the base and trees will reward you with vigorous growth.

Check under pruning to see what MSU recommends for sour cherries. Ton's of different techniques to train cherries exist. We have more sour cherries here than any other state.

Here is a link that might be useful: Pruning info from MSU

How interesting. I do have 2 dump truck loads of mulch about 100 feet away, so I can easily mulch and was planning to do so. But I had no idea it would make a significant difference. I did read in a recent thread that it might increase vigor some, but I assumed it would be minimal, and there was some debate on if that was even a good thing or not. I assumed mulch would just be a marginal difference. Same goes for controlling grass other ways (ie glyco, which has also been recently discussed here). Again, I didn't think it would make a big difference. Since grass grows close to ground and trees much deeper, I didn't realize they competed that much. I also never thought about having to tie netting down at the base.....I thought you just put a net over the top and let it hang down. I guess birds are more determined than I imagined! But I am 100% certain I will have a bird fight on my hands....my (very) nearby wild cherry trees are absolutely covered in every kind of bird imaginable during fruiting time.
Finally, I'm especially shocked to hear you say to cut other large branches. Please explain that a bit....I mean, are you saying only those coming off the central leader so it will just be s straight stick up the middle, or does that include all other branches on the tree? Surely you aren't suggesting at this point that I should cut everything on the tree except one central leader so I'm left with nothing but one straight pole? THen again, as little as I know, maybe that is what you are saying?? Thank you both. I'm going to look at MSU's recommendation right now.

As I said in my post ton's of ways to prune cherries. What harvestman suggests is one way. I myself use the KBG method for sweet cherries. I don't have any large tart cherry trees yet. I'm trying to grow some at my cottage, but I actually doubt I will succeed, the conditions are too harsh. I don't have enough good places to put them. Parts of my yard left are too shady or too wet.

I was explaining a general method of pruning them similar to what I do with all fruit trees when I talked about ratios. When you are training trees to a low open center this method is entirely optional but there are complicated reasons why understanding ratios can be useful. If you e-mail me I can send you a paper I wrote some time ago on the subject.

Do you understand what I mean about inverted bark? Those are the only large branches that I think are important for you to remove regardless of ultimate shape. It's pretty much Pruninig 101 and universally accepted no matter what literature you go by.

Grasses have roots exactly next to the important feeding roots of trees and grasses exude chemicals to weaken trees and often vice versa. Grasses have massive fibrous roots that are very hard to compete with even if you exclude the factor of alleopathy (exuding poison).

When establishing trees you want maximum vigor, when they have reached near desired size you generally want moderate vigor for highest quality fruit and best yields.

Harvestman, I sincerely want to thank you for taking the time here and other posts to help this beginner. Its clear that you are an advanced fruit grower and have undoubtedly answered questions like mine countless times over the years, which makes it all the more impressive that you'd take the time to once again address my questions. I must confess that I do NOT know what inverted bark means, but like most replies I get here, soon after reading them I'll go and do additional research. WHile winter dormancy is generally a boring time for my and my gardening/fruit growing, the one good thing is it gives me time to do such research. Thanks again. I'll be sending you an e-mail to get a copy of your paper on ratios. The info on grass was also interesting to me, as well as somewhat surprising. When I dig a hole for a new tree, the turf/grass roots are incredibly thick and fibrous, as you said, but they only seem to go down about 2-3 inches. My tree roots, on the other hand, are planted down 18 inches or so and I assumed stayed that low, so I didn't think grass roots and tree roots competed that much. I have kept my grasses at bay around my trees (via glyco) but thought it was mostly for appearance. Also, just as I read in a link on here from Olpea (I think), after I keep grass at bay for a while I tend to get clover or some other growth around my trees. Guess the battle never ends! Thanks again.