Adjust your mock-up to 36 inches over the range/cooktop. Determine head hazard as a function of front-to-back depth. 27 inches hood aperture is good, but if you keep the high momentum plume cooking toward the rear, their plumes' escape will be minimal with a lesser hood depth. Note that few off-the-shelf hood inserts are as deep as one might want. Wolf's largest is 22-5/8 (wood cover excluded). Your decorative trim is a driver for safe hood base height above the countertop.

We can discuss CFM of hood system and make-up air system once you have selected your hood.

Aim for what is available and affordable. The affordable 90% solution is more effective than the 100% unaffordable solution.

The appliance store recommended this oneXOI3315KSE by XO. I think that is actually only 15" deep. Honestly I can't believe what a production it has been to figure out what hood insert to buy. Between the dimensions, the CFM info, etc etc. and the range in price, it is overwhelming. Plus no one at the 3 stores I went to seems real knowledgeable. I wonder if I am overthinking this!!

@User so you think I should look for an 18" deep unit? The GC is prepared to install the MUA vent etc. How do you feel about XO products for vents in general?

No, 18" deep also is too shallow. At least get a 24"D hood. Ours is 24"D and captures all the FOGSS on the front (and back) burners. (FOGSS = Fumes, Odors, Grease, Steam, Smoke)

Regarding hitting your head -- most people do not. We seem to have an inherent "sense" when something is close to our head. If not, you develop it quickly. I do know that we don't hit our heads on ours. My family ranges in height from 5'10" to 6'7" and we're all fine with the 24" deep hood. (It's mounted 30" above the cooktop.)

In ranges, the cooking surface isn't the entire depth of the range -- the oven doors stick out farther than the cooking surface. So, 24" should cover the cooking surface plus a couple of inches in front (which is what you want).

IF this were an island or peninsula installation, then a 27-inch depth would be needed since you would need extra space beyond both the back & front of the cooking surface.

Ours is 22” deep and 34” above cooktop. the 6’6” person in our household is always turning on the touch sensors with his forhead. really wish we had done 36” up. we are very happy with the venting (a lowly 650 cfm…). but you might want to leavr that box up for awhile - not everyone gets used to it :).

One thing I would suggest is to grab your tape measure and go to a large appliance store or kitchen showroom and see what sort of hoods are on display. measure the depth and see what you think. Then work on the rest of it.

Then go home and pay attention to when you are cooking. How close are you to the stove? You said you taped something up so you could feel the depth, but did you try cooking with the stuff taped up? It is the only way you can tell. No one cooks with their belly against the hot stove.

Also, most exhaust units can go up to 30" above the cooktop - 36 may be too far, Plus you will be looking up at the guts of the unit all the time when it is hung that high. Not terribly attractive.

Don't overthink it, but don't panic over it.

@Buehl I guess I am not worried about literally bumping my head, but feeling like I can’t get access to what I am sautéing etc.

@Debbi Washburn good idea to go to a display room!

My current stove is in the island with nothing above it so I can't really mock something up there. Our old house had a microwave/vent combo that did nothing and I honestly can't recall how deep it was.

I am definitely overthinking things ;)