Ummm dunno about the tranny idea ... but hey I got a daft bumper on my bus so don't suppose much different really .

I still say use fibreglass to make your mould as you may well bop both and need to make new parts, the plaster stuff is really only for one pull from the mould to capture the design.

What you need is someone who knows how to play with grp to point you in the right direction