Lightweight hulls must be worth a lot. Else, why would someone shell out $2500+ for a Kevlar/carbon hull when they could get the same thing rotomolded for $1000.
The problem is more than just added weight. Another thing not often contemplated is the amount and duration of all the sanding required to prepare a hull. Using harder species of wood can make hull prparation more difficult. And if you don't have a dust collecter on your sander you'll eat alot more dust.

: I'm a newcomer to the list, and my wife and I have been kayaking for several
: years. I currently have a Wilderness Systems Cape Horn 17' and 16",
: an Old Town Egret, and a Pungo. All plastic boats. Now I have been bitten
: by the building bug. Got ahold of The Strip- Built Sea Kayak and am
: devouring it. I'm a woodworker by trade. I mostly make doors, many of them
: hand carved. So I have the space and the tools. I also have a lot of
: mahogany and alaskan yellow cedar left over from past jobs. My question
: is... if I use the cedar and mahogany how much weight am I going to add if
: I'm building the Guillemot, compared to a lighter variety of cedar, or
: redwood? The alaskan is very dense and does not resemble what you
: ordinarily think of as cedar. You can't nail it without drilling a hole.
: Thanks and nice to be here.
: Gerry