Leon,

Perhaps I'll get it right this time.
I have built a Sea Tour 15 for myself at 5'9" and 24o#. I thought I needed to move the seat about 4 inches fwd of the rear of the coamming to get the boat level (slightly nose high, instead of a lots nose high). Seemed to float well with me.
I did make a 4" longer cockpit to let my old knees fit easier in the boat. This is rather a pain in trying to figure out how big to make the moved #3 frame.

I ordered 17' of cloth (8oz.) from Dyson.

BTW, my son and I are making another 15 to teach him how to build a SOF. 4 days and we have the frame ready to epoxy in place.

Marc