RE: .21 Zippkit ready to go
The fillets I created are 1/3 the size of that of balsa. I doubt I added any weight at all. However, structurally I added more integrity. Once cured this material has a shear strength of 3500 psi between blasted steel. Yes a bit over kill academically for this application but with its non sag vasoline consistency its easy to work with.
I am at a standstill for now on the tub until I get my motor, and I can't start the sponsons until I get the missing plates. So things just came to a screeching hault!
I am curious as to the weight difference of your sponsons. I am not going to go through the seal, sand, prime, paint and then clear coat. I was thinking more a long the lines of adding a tint to my epoxy clear coat to get my coloring. It doesn't take much to tint the material. It will be both my prime and top coat.