I'd second a Toddlease if you want to try a simple popper one that has room for lots of boosting Steph.
I have a big stash of large Sandys but the standard ones are starting to get a little tight on the thighs, the organic ones seem bigger and he still has growing room in them! They are really thirsty too and I can boost with a folded muslin if we are going out and about.
Edward is around 28lbs and has big chunky thighs too - 12.5" ish at the moment, so a lot of large fitteds are too small for us
Puddlepants nappys are so pretty, if I had a girl........