After making the second fat suit, I realized that the method I used to make the first fat suit really wasn't going to work. So I ended up taking the Edna suit completely apart, drafted and attached new sleeves (the director wanted them a bit longer), and put it back together again. But this time, rather than just stuffing the cavity with loose fill, I constructed pads out of batting stuffed with polyfill to make the bust, belly and butt shapes. This worked out so much better!
I brought the suits to rehearsal yesterday for a second fitting and the director was quite pleased; she had the actor try on a nightgown over the fat suit and it fit (size 3X)!
I still need to tack the shaping pads into place and take just a smidge out of the belly pad, but overall I'm happy with how it looks and the actor is quite comfortable in it. I also took measurements with both actors in their suits so I can start making the actual costumes (Five for Tracy, three or four for Edna).
Some of Tracy's costumes are blouse and skirt combos, but rather than making them as separates, I'm going to make them as dresses, with invisible zippers up the center back seam to make quick changes a lot easier. It will also insure that the skirt stays put; the waist of the fat suit is squishier than an actual body and I'd be afraid of the skirt falling down.