After several learning-curve evolutions, I finally managed to download & (somewhat) learn how to use Ross Leidy's Kayak Foundry program. You get a diagram that looks like this:
By moving points around, you change the shape of the kayak.
It kind of reminds me of when I used to order e-juice from E.C. Blend, put all my preferences in, and get a juice that tasted perfectly lousy. I have the ability to put in all the measurement that I think I want, and also make my own mistakes! "Tiny" changes will make a huge difference in the feel and performance.
Interesting feature: you can print out the forms scaled-down, for example 1/8 size, and make a scale model. I tried printing 1/6 scale, but the forms seemed too tiny to work with.
I also bought Rob Mack's' instruction manual for building his "Panache" kayak. In e-mails, he describes build on a "box beam" strongback, and I had to get the manual to see what he means. It looks like a long box girder made of plywood. I'm also considering, if the self-design becomes too scary, building another full-sized Outer Island. If the box-beam thing turns out to be a sweet & solid way of aligning the strongback, maybe I can avoid another blunder.
One of the cool things you can do with the kayak Foundry program is print the forms out at reduced scale, and build a scale model. I tried printing 1/8 scale, but found the forms to be too small to work with, so I tried 1/4 scale:
Ross did this for his RL-1. He went "all the way" in construction, even fiberglassing the hull, but I don't plan to be that fancy.
Actually, I found it harder to work with strips on a small scale, and I have shelved this project for now.