25 kg EPS foam/ wood stringer / 6 oz glass on bottom/ 6 oz on deck ant 2 layers carbon 200 grams under grip position .
Will be light around 8kg/ strong to snapping in halves / strong to print stepping/ enough strength to paddling shocks as well.
Hand laminating might be easier than amateur bagging which can be disastrous for rocker/ stability during bagging process.
Put one air vent on both side of stringer
This is my thought about it