If you want a Chassis, the Oryx is about the best deal. Fits AICS mags and it’s ready to go out of the box.

Oryx
https://www.tacticalworks.com/oryx-c...on-by-mdt.html

Step up from there you could get the XLR Element Chassis.
https://www.tacticalworks.com/Elemen...ndustries.html

An “In Between” would be the MDT XRS. It’s sort of a cross between a “stock” & a “Chassis”.
https://www.tacticalworks.com/xrs-ch...04692-blk.html

*EDIT* BYW, I’m in the same boat size wise. I’m 6’4” and about 275lbs now. (Was 230lbs in fighting weight). I’ll say this.. it’s better to adjust yourself to your gear, rather than adjust your gear. I was an instructor and constantly harped on this to people. From Grip, to LOP to Stance. Shooters are forever trying to get “comfortable” when they are shooting. And I can tell you, if it feels comfortable, you’re most likely doing it wrong, LOL!