Whoops, thanks zirconmermaid! I completely forgot DM had two sizes of FMDs... I just knew one of them came in both vinyl and resin.
For torso support, you could look at an opened-up Obitsu/Parabox hybrid and do something similar to that. A single-piece torso would be easiest, since you need multiple rigid parts on the inside, but there are probably ways to make the interior more flexible while retaining the structural strength... it might need jointing, though.