Revell didn't really think of the poor modeller much when they designed this kit. Flipping the kit on it's roof, I find that there are all sorts of gaps underneath that will let water in.
Since this will be detrimental to the finished models performance I've been stuffing them with bits of polystyrene and then sealing this in with epoxy glue. Some of this has been run around anywhere I think water might make it's way in.
Lets hope it works. I think on the real thing they used filler foam and killed the engine.