So I rode the gondola up with a younger couple at Stratton the other day, and they were telling me about a gymfest center in Brattleboro (I'm pretty sure they were affiliated with it). They said there was a 20 x 20 foam pit, in-ground tramps, etc.
I don't remember the exact dates, but I think they said adult open gym was Tuesday nights and Saturday afternoons. They asked me to spread the word, so if anyone is looking to do some cross-training definitely check them out.