You can see some pics in my progress thread here:
Progress Thread
The largest I could get was an XL - it's tight/snug but not uncomfortably so. There is a lot of stretch/flex in the suit. I removed some of the extra elastic strapping from the forearm section for a more comfortable fit but other than that it's pretty much stock. As a frame of reference I am 5'11", 200 lbs, and have a 47" chest and a 36" waist. I think that it should fit as snugly as possible without being uncomfortable but what size would be best for you - I don't know...
I think that Skullcandy Girl found these first and currently has one but I know that she's a whole heck of a lot smaller than I am
I don't know who else jumped on the Sette bandwagon. I can say that I like it more than the 661 suits I've seen...
Good luck!