|My dd is 5 months tomorrow. Not sure how much she weighs now, but was 16 lbs at 3.5 months.
I moved her up to the M/L a good while ago, but have the same problem you are talking about.
I have to put it on smallest leg size otherwise it seems gaping, and the waist is 1 in on 1 side, 2 in on other. I dont think dd can go up to the L yet.
I had prefered the airflows till recently but now like the rikki better. However, we use pfs most of the time and they dont fit in the rikki with all the bulk. If she has on a meos, I use the rikki wrap or a lite wrap.
KRISTI; BFing, CDing, BWing, co-sleeping, selective/delayed vaxing SAHM to Kailey Noelle 12/24/94, A. Thorne 1/20/01, Henna Claree 1/24/05, and Caris Aoife Lachlin 10/16/08.