Wow, thanks, JAK!

One thing I've learned while doing my reasearch is that most, if not all, of the late kayak designs are done on boat CAD software. Hopefully, all those parameters you mentioned are taken into account in the design. I've designed/optimized telescopes and antennas this way on specialized software....it's a big time saver. The 'offset' tables are in decimal inches, which has been a pain, so I converted it to metric. I've never worked with "offsets" before, so this is a learning experience for me.
Two things concern me about building such a low volume, skinny boat....my weight (180ish) and the fact that salt water is 5 hours away, meaning, I'm dealing with fresh water displacement. This boat is designed for a 190 lb. driver, and assumes 15lbs. of gear. I'm hoping that gives me some headspace in the design.
The boat I'm building is designed and used in the Denver area, so fresh water is the medium. It's also a 'low draft' design, meaning not much of it sticks out of the water. This is good in that wind won't effect it as much, but I better be wearing a skirt or we'll become a submarine.
Like all my boats, I'll stuff all open space with pool noodles for flotation, and to take up volume. A sea sock is recommended....still thinking about that one.
I've decided I don't like hatches...my three yaks all have 'em...but I think I can save weight and headache by using drybags instead. I'd rather have deck perimeter lines and bungees on top, instead of fixed hatches/bulkheads.

My 13.5' boat is 23.5" beam, is flat bottomed with a 1/2" keel, and is quite stable and fast. With a bit of rocker and the extra 2+' of wetted area, I'm thinking 19.5" inches should be manageable...a little better than a surfski, since my center of gravity should be lower.
I'm thinking of lengthening the design slightly and raising the combing a tad. That's the enlightening part of skin-on-frame....you can change your mind in the middle of the design.

I'll try and wrap my brain around all this.

Jim?....software? What's recommended??