My sister gave me a bamboo one of these the other day as she had just bought some and the leg elastic was quite big on one - far too big for her skinny thighed LO - so gave it to me for Charl (big thighs).
It seemed a bit gapey on the legs even for Charl - tho thankfully it didn't leak - i ended up having to leave Charl in it for quite a while as we were out and i didn't have chance to change her - and i was surprised when i got home that it was only about 2/3's wet (with the extra booster). I washed it earlier and it is now in the drier! So am not sure about stuffing.
I think if I had bought it tho i'd have returned it to tots bots to get the leg elstic sorted!