I'd be interested too but mines gen1 and not quite the same tank.
I don't see how they would damage the tank. All they will do is use hot glue to attach a very thin plastic fin all around the tank front to back, top and bottom.. this fin passes transversely through the mold they will make next. The fin divides the mold so the mold can be separated into two halves without cutting it. if shape is irregular enough to require a 3 or 4 piece mold, there would be additional fins passing through the mold to accommodate. They will smear vaseline on the tank and fins for a mold release agent, coat with a few alternating layers of cloth / liquid latex rubber, then encase in plaster ~4" thick.
Everything is pulled apart immediately after the plaster hardens but before it dries enough to shrink. The plaster is called the mother mold because it supports the latex/fabric conglom mold which is the actual copy of your tank.
smear inside of latex mold with vaseline and now fill each half with clay probably use some lightweight material to fill inside to reduce weight. Stick halves together, remove mother mold remove latex mold...voila--copy of your tank. Shave down or reshape any way you want. --or you could cast it in plaster if you wish but clay is easier to work with--you can't stick new plaster on old plaster so once you carve away plaster, its gone.
Now you take your clay race tank and repeat the mold making process with fin, latex and plaster. Sepparate mold and coat inside with fiberglass or whatever composite they use.
It would be a job but quite fascinating if you have the time. Could do a few practice runs on smaller objects to become familiar with the process. One thing you have to watch for is shrinkage. Plaster shrinks as it cures and clay will do the same as water evaporates. The larger the piece, the more it shrinks and a fuel tank is pretty large. I could see it losing an eighth inch if you let the mold or casting dry out too much. Bolt holes need repositioning probably solve that without much trouble if you worked in clay. The final composite tank probably shrink a just a tiny bit too. Just about every casting material does.
so maybe you be better off letting fuelcel do it. unless you want to go into competition with them...what do you say, Cool you and me go into the composite bodywork biz?
'08 MIDNIGHT SAPPHIRE BLUE Now Deceased