I considered two options for my LED suit wearable panels. PVC, most likely from a central vac pipe (which is thinner than typical PVC pipe), cut down its length, flattened, and cut to size, OR cardboard.
I ended up going with cardboard because it was ZERO cost. I chose cereal box cardboard because it's thinner, but denser, than other cardboard. Another option I considered was old file folders. On its own, a single layer of thin cardboard wasn't strong enough. Also it was flat, instead of the curve I wanted. The solution was to laminate two layers together.
I cut the pieces of cardboard to the desired size. I don't recall what that size was, at the moment, but I'll measure them and add the specs later. Basically, I measured out the space a 6 by 12 LED grid would need, and then added some extra around the edges.
To laminate the pieces of cardboard, I used some "puzzle saver" glue that my wife had leftover from a different project. I experimented with one panel first, and it worked well, so I used the puzzle saver for all the panels. Another option would be ordinary white glue, SLIGHTLY watered down.
All you need to to is apply a thin coat of glue to one side of one piece of cardboard, and lay a matching piece on top. I put the plain, unprinted sides face to face thinking the glue might hold better than on the smooth printed side. It probably doesn't matter though.
TIP: Place the two pieces face to face WITHOUT glue, and then use a couple of small pieces of masking tape to make hinges on the outside on one edge. Then open it up to apply the glue. Once the glue is on, it's easy to close it and have the tape hinges line things up.
When you put the glue on, the piece will probably curve. It's nothing to worry about. The surface with the glue is expanding slightly as the it soaks in moisture from the glue. Simply assemble the two pieces and move on to the next step.
As soon as the glue was applied, I fastened the laminated piece to a curved object that had the same curve radius that I was after. The tightest curve was for the forearms and shins, a bigger radius (a paint can) for the forearms and thighs, and a very wide curve for the chest piece. In hindsight, I probably could have gotten away with a flat, or flatter chest piece.
The chest piece was sized to allow two grids, side by side, and the space between the grids is the same as the space between all LEDs.
When dry (at least overnight, preferably 24 hours), the panels held their shape amazingly well.
I decided to give the panels a coat of spray paint to help seal them and keep the glue dry. I would recommend regular spray paint but, since I had some sitting around, I used a rocker panel guard type of paint. It gives a cool, orange peel kind of texture but, in the end, smooth would have been just as good, if not better.