kaseki, Thank you for your input. I have lived in this house since 1981 and not ever had any insert/fan/liner, etc. I cook quite a bit but not a lot of greasy stuff. I am mostly vegan and so there is a lot of stir fry type of cooking. I also bake quite a bit which is one reason I want the dual fuel.

One question regarding your suggestion--If I were to center the insert over the range and put stainless steel over the other part, would that present a problem for the duct since the duct is centered in the "boxy hood thing"? By this I mean that the hole where the duct goes up to the roof is at the center of the box so if the insert were to be centered over the stove, the mouth of the insert that fits into the duct would not line up with the hole. I hope this is clear. Is there a way to connect the liner to the ducting by possibly doing some type of elbow connection? I have really no idea, I am just thinking about it visually.

One other thing I had thought of is that the boxy thing is pretty high (about 37.5 inches above the counter). Would it look odd to build on it a little by either adding some trim or molding around the edge to extend it down a little more? Another option would be to get a regular hood of some type that might work with the box. Not sure what that would be, maybe a standard low profile vent a hood or perhaps some type of wall type hood with a long neck that comes down and flairs out below the box over the stove--it could look good or it could look really weird.

I understand what you say about losing all or part of the boxy thing. But this house is very old and I have literally resurfaced every bit of it over the years. You can't do anything without opening up a huge can of worms. I am already spending quite a bit to redo my electrical panel and have a 240 outlet put in so it isn't really in the budget to rip it out. Being a perfectionist at heart, it is tough though for me to be okay with good enough, but I think on this one it will have to do. I suppose we could always close up the bottom of the box except for the access to the duct and just attach a lower profile hood to the bottom of the box (likely centered over the stove).

Duct elbows exist, and a pair of 45-degree ones that have rotating parts can be manipulated to address any offset, given enough height to fit, optionally using an intermediate straight section if the offset is large.

A low profile hood of sufficient size to overlap the stove top (side-to-side) and overlap the front burners (if possible) could be used, and would bring the hood base down to around the typical 30 inches of smaller hoods. This would leave a lot of room for the duct offset to be accommodated.

Flow rates of such hoods will generally be inadequate for hot cooking, (searing, grilling, and wok cooking), but might be OK for stir frying vegetables so long as temperatures were low enough to not vaporize avocado, grape, or peanut cooking oil. I.e., not attempting caramelization.

The GE Monogram, be that all propane, OR dual fuel, is excellent. It' a glorious machine in fact and the oven will hold a full size catering sheet.

It is WORTH the money to investigate removal of the "box" and get a hood that truly works. Frankly the all propane model suffers NO loss of function, at ALL.

You’re not connecting any hood to a 4” duct. That has to be replaced all the way throughout go the roof, and an electrical line has to be run. There’s no getting away from that.

You might just just look at a standard under cabinet hood with a bit of creative carpentry. That all is going need to need to be opened up anyway.

The duct is 6 inches. I already had my installer who is very experienced take a look at it. He just did something similar last week and says he encounters these all the time in older homes. He gave me several options for inserts and inspected the duct situation up to the roof. But I am beginning to think that a standard under cabinet hood that centered over the stove is perhaps a better option with the use of the proper elbow or straight duct to accommodate the offset. I believe there is room as the hood is quite tall. Another issue that an under cabinet hood would solve is making it so that I will be able to reach the light and vent controls easily. That was something we were a bit concerned about with putting an insert up in there. We might have to put a switch some place if we go the insert route. Or else get one with a remote. The under cabinet hood might also extend out slightly over the front of the stove whereas the insert will not.

Thanks for the reassurance regarding the Monogram range--it will be dual fuel with natural gas. I kept looking at the Wolf because everyone seems to lavish praise on it. But the price for the duel fuel is about $2000 more and I just cannot justify it. I have looked at and researched everything and feel like I could go into appliance sales at this point. I go into the stores and I know more than the salespeople which is really frustrating. I don't know how these people get these jobs when they know very little about what they are selling. When I found my installer it was a breath of fresh air because he knows the ins and outs of all the ranges and he said the same about the Monogram. So I am starting to feel comfortable going that way.

Just wondering live_wire_oak why you say "that is all going to have to be opened up anyway"? I am certainly not wanting to do that and had not planned on that. But want to know as much as possible so all can go smoothly when the time comes to do the installation. I do appreciate all of you for taking the time to share your expertise with me.