I had planned to scratchbuild them as well, but time is ticking. I'll use them on this kit for now then pass them on to my wife for hers when I get this one "done".
Also, for posterity, the pipe insulation tubes survived the fiberglassing wholly intact. I saran wrapped them to a 2x4 and dumped resin over them. after it cured, the resin had dripped down the sides attaching the plastic to the cardboard I had laid under it, but the 2x4 slid out easily and the foam was perfectly fine. The plastic wrap was wrinkled so it didn't pop off perfectly, but the parts that were smooth on the edges proved that the resin would not stick. I'm calling it a successful proof of concept and moving on. a little research also stated that resin will not stick to duct tape so here is the plan:
I will duct tape the tubes in place against ZAPPA's sides to create a gap between my actual stomach and where the shirt will rest. Saran wrap the whole torso tightly. Slip the v-neck shirt onto ZAPPA over the new spacers, possibly having to remove his arms in the process. Mount the plates where they are supposed to go using tape. Resin the outside of the entire chest/shirt/back area with a couple (three?) layers. I'll have to see how strong it is at that point and go from there as it will be getting manhandled quite a bit int he next step. Once i am convinced that i can get it off without destroying it, I'll cut/slide the entire thing off in one piece if at all possible. Where the shirt meets the plates I want to keep the excess and resin it to the bottom/back sides of the plates to make the joins as solid as possible. Where shirt doesn't meet plates it will be trimmed and shaped. Hopefully I now have a single piece upper torso. The inside of the whole lot gets a couple layers of fiberglass cloth for unified strength and start in on the outer bondo and back to the fun game of bondo, sand, bondo, sand, bondo, sand, beer, sand, bondo, sand. There will almost certainly be a ZAPPA mk2 made in there somewhere so that i can mount the plate and work on them while worn I think. It seems safer for the plates than pressing down on them and taking the chance of snapping them.
So, anyone with relevant experience care to either confirm my concept or correct me? I am hoping to get started on that process come Tuesday.