Maybe a bit late here, but something else that works is to cover the open bays with Solartex, then paint everything with System III paint. It is a WBPU boat paint, so it is waterproof, and with the cross-linker added, is fuel proof also. There is a good thread about this paint over at RCG.
Also, I found that Minwax makes a polyurethane sanding sealer that I like to use before the System III paint. I've had good results so far using the sanding sealer and no primer.