Okay, time for me to chime in on this one. I see some "questionable statements that I think need to be addressed:
1) NEVER USE BALSA IN A HYDROPLANE FOR STRUCTUAL PARTS!!!!!!!!!!! Balsa will not handle the pounding the hull will take. Notch the frames and install a solid SPRUCE stringer instead
2) HAIR SPRAY IS WATER SOLUBLE, DO NOT USE IT AS IT HAS WATER IN IT THAT WILL SOAK INTO THE WOOD Aircraft dope is a much better alternative as a lightweight sealer if weight is that much of a factor and epoxy isn't an option. Better still is that it's fuel proof
3) CUT LIGHTENING HOLES IN ALL UNDERDECK FRAMES, this will cut your boats weight by up to 40%
4) Build your boat from 1/16th ply with 1/4 ply transoms. You wil save another 35+% in weight
5) HOT GLUE??????????????????????????????????????????? NOT IN MY BUILDS, EVEN TO TACK. If I want to tack something, I'll use CA so there is no question about the part moving