A TypeII vest is a semi-mythological creature, no one has ever seen one in real life.
A Type3 is going to be uncomfortable even if you're not, ah, chesty. For comfort people buy Type5 inflateable PFDs, preferably an auto-inflate with built in harness and crotch strap. You can wear it "slack" as long as you've take the important step of actually inflating it (by mouth is OK) in the water to make sure it will fit right when it IS inflated.
And FWIW, an inflateable shouldn't be worn unless you're willing to CHECK IT from time to time, to make sure it holds air.
Yes, every brand and model fits a bit differently, but AFAIK
none of them come in "portly" or "chesty". Although, maybe that's a sales opportunity for Maidenform. :-)