You might want to review its cost vs a new hull?
If you've already cut them out to bare glass and your hull is now a piece of vinyl to flex in sun, good luck! Flat concrete and couple real jacks needed before any wood work.
If you've cut the tops off and washed the channels real good then epoxy the new wood in, widdled to match.
Then glass in the lag with 1708 mixed with chop strands in the same day. It can be done but remember all bolts to the stringers except poly.
If you not sure about gel coat or it might be your next post, just buy a new hull and be done and boating.
Your anchoring your entire power system from free advice and nothing of the bottom of it, which should be next after proper stringers, If they were correct to begin with?