I have used Kayak Foundry to design and build about fifteen craft; several sea kayaks, a TK1, two K1s, three children's kayaks and a TC1.

If you post up your design on the Blue Heron Kayaks site on the "Kayak Foundry" forum, I guarantee you will get helpful responses from people who have used the program to design and build kayaks.

When you do that, I will tell you what I think about a SF of 73. :)