" That's what I do, fill coat only the cockpit/foot well areas. The unfilled glass is a bit too abrasive for me in those areas, not needed in the ends. "

Plus you pick up sand on your shoes and grind into the weave of the cloth and it gets trapped there.

The age-old strength vs.weight question.
The lightest boats I have built were stitch and glue. My first Chesapeake boat was back when Chris Culziki (sp ?) owned it and his plans called for no glass on the boat other than taping the seams. It was just coated with epoxy. My brother still has that 17 ft. 23 wide kayak (Cape Charles) and its just over 30 lbs and plenty strong. Every now and then I take it out and overall an enjoyable boat with no bad habits. It cold be made lighter with a lighter coaming design. I made a 17 S&G rolling boat which came in at low 30s.and I could have saved 8 with no bulkheads or hatches. I used Becksons on that.