[Ant]

With all this neoprene and other glue in foam type protection, may retain water but should deflect stones etc!
What I have seen done with some kits is a double skin of fibreglass with a small gap between layers, this will add some weight, and will have to be thick enough to withstand a bit of punishment, and it could also be covered with an average coat of rubberised underseal!

I could get into the area of overkill here, the old KISS principle of keep it simple stupid applies, but I hate paint crazing due to stone damage!