For what it is worth here is some other things to think about.

There are two ways to achieve more stiffness. One is to add more layers, the second is to separate the inner and outer layers by a core material. The separation of the layers is what allows fewer layers then a pure glass. While most of us use strips or plywood as a core material, the very lightest and stiffest boats are carbon fiber around a Nomex honeycomb core. Nomex honeycomb is actually made out of a kevlar. Others use special foam cores to achieve separation. The high end crew shells and ICF racing kayaks are constructed this way. I suspect that without a female mold vacuum bagging setup we won't be making any of these in our basements.

The other problem with these boats are that they are very fragil to impacts from sharp objects.

Jack