I would like to think I'm the king of little keeper sleepers, I own 12 pairs. The quick and easy: I am 6ft about 192lbs with a 34 / 35" waist, size 10 1/2 , 11 foot (depending on type of shoe / boot. I am also fairly proportional, meaning no large belly or butt. I fit size 18 just about perfectly (there is a size 20 and I would imagine that it would swallow me whole)
These sleepers once zipped and snapped are hard to get out, the zipper is funky to get all the way up if you don't have a lot of flexibility. The 3 snap buttons aren't that bad to snap, but once the sleeper is on you will def feel secure and the strength of the garment is very apparent. The sleeper is designed to be tight to your body, its a fairly snug fit and the cotton will stretch / mold around your body, in the design of the sleeper they leave the seat area large enough for a thick diaper. When wearing these it will be apparent that you are diapered, there is no hiding that fact (this is why my girlfriend loves these)
So out of a five star rating for these sleepers I give them the full five stars, the price is fairly cheap compared to other adult pj's, fit is excellent, strength / quality of materials used is great.