While it's true there are some hull designs that used foam and even cardboard forms to shape the stringers, in our boats the wood "backbone" in the framework is structural. IE: it needs to be there for strength. Unless you have a mechanical engineer design a better method, I would stick with what Glastron used. Granted they could have done a better job with the quality of the glass work in many cases, and Lord knows the drain positioning could have been better, but stick with the original design on stringer composition. (The only possible exception would be composite materials like King Starboard or "Tuff Board", but I have no experience with those. Others like Doug may be able to advise more on that subject.)
I encapsulate
all wood in CSM then tab it in (and over) with 1708 biaxial, water should never get to the wood to start the dreaded rot process. NO SCREWS thru or into the floor after the last layer of fiberglass goes down, moisture will work it's way in eventually. Properly treated, installed, and maintained the wood should last longer than most of us!
Just my humble opinion, it's worked for me.
