You've made it large but you'll have to change the grease cup and filters with a ladder. But that's doable. Sounds like you're not using induction so it'll remove waste heat from gas too.

Looks good (great) to me from here (NH).

:)

Four feet by five feet = 20 sq. ft.; you will likely need an up-blast roof blower capable of pulling 1800 CFM through that baffle set and the ducting, and this will likely require the blower be capable of 2700 CFM in free air. MUA ditto. Review of the Greenheck guide is advised if not already internalized.

If I go in this direction, I will likely modify the hood so that the duct for extraction is on the side rather than the top, and use a side-blast blower. Due to the location.

Not figured out MUA but easiest would be floor register under the range, due to ease of ducting through basement.

Should work. Care is needed to ensure that the MUA leaving the register gets into the kitchen without causing a transverse draft above the burners at the plume volume that disturbs the plume such that it is deflected away from the hood. This can happen if directed onto a near island or peninsula. Note that a diffuser is better for directing air flow than a register. www.hartandcooley.com

Also, cutting a large enough hole for that level of MUA should be complemented by accounting for the structural needs of the range weight.

Did you install this hood? I am thinking of doing the same and would like feedback.