I don't have quite the same problem, my issue was being 6'9" and not fitting. I ended up doing a custom suit from Kokatat. While it came out fine, I think if I did it again, I'd have had them do a XXL waste on the top and add another inch or two to the inseam. Fits fine, but the crotch is a little low and the waist a little tight (and I'm thin at 210lbs). The waist surprised me as it's narrower than their XL drytop I have. It fits fine, I'll be in trouble if I gain another 40lbs I suspect.
The overall cost adder wasn't too much, couple hundred if I recall. Been one of the best purchases I've made. Kokatat was easy to work with, though at first they didn't think they could add the additional material, after talking more with them they said yes.
But I can't really say how a XL vs XXL drysuit is, but custom wasn't too bad. I'd note all my comments are on their GMER suit, not the new Jackson one.
"Basic research is what I am doing when I don't know what I am doing." -- Werner von Braun