Update: I did the 2-part pour-in foam. It didn't stink, but I waited until we had a nice hot day in April and I did it outside. I used sliced up pool noodle to keep the liquid from going under the gas tank or wherever else I didn't want it. Glad I went with the structurally-solid option that adhered itself to the floor. I've since replaced the transom and nearly everything else on this boat - hoping to take it out for the first time since rebuild. For anyone reading this seeking wisdom: I saved quart yogurt cups for months. Glad I did - I bought a 12 pack of mixing cups and burned through them pretty quick mixing small batches. I used drill to stir it - the $6 paint stirring attachment is worth three times that price! Also, once poured - don't mess with it. I tried to smoosh it from one place to another where it got too big - anything I moved or poked at became dense and plastic-y. would have been better off just to leave it and cut it off later. I made a long C-shaped handle and screwed a section of old band saw blade to it - worked great to slice off the foam even with the floor. (I did this with floor out - didn't want to cut access holes in aluminum floor) Supplemented the pour-in with pink foam board from hardware store. Stashed chunks behind interior panels too. Any seams or holes in the aluminum floor I caulked shut to keep water out.
Hope this helps someone.
