HI,
I know its not a vac formed plastic hull, but why not try a mini-springer. For myself i found the 18" std springer a bit big, so designed and built my own at 12" long.
That's 66% size. They are very easy and quick to make, mine all balsa, but any cheap ply and scrap wood can be used, just seal / paint it well, and it will withstand any sort of abuse.
Mine uses an off the shelf motor, coupler, shaft and prop from the local hobby shop, can run on anything from 4.8 to 7.2 NiMH rechargeables, and I use a very cheap 2.4Ghz 4-channel r/c unit.
Springer plans are free, and you design whatever you want in the way of superstructure.
Simples
cheers
vnkiwi