Dude... about waterproofing... yeah if you are going to mount the crossovers in your doors I would waterproof them. With the midwoofers... www.crutchfield.com sells XTC foam covers for the rear of the speaker... to protect it from the environment. but most speaker cones are waterproof by nature... I'd use the XTC on untreated paper cones.. which are pretty rare in car audio..

I would not surface mount the tweeter..because it looks BUTT ugly I would recommend flush mounting the tweeter by making a very precise hole and slipping the flush tweeter mount into the hole... u'll get a very clean install!

Good luck and let us know how it goes