1987 Valero YT Bowrider...need advice

[tunnels]

When making stringers , the what ever you making the stringer out of is not important and can be any old thing its the glass over that shape that's giving you strength and durability not the core you going to use ! the shape is what's the important part in reality polyurethane foam is cheap , easy to shape and is what can be used not a problem

Like I pointed out glass over the core with 1708 before then mount you stringers on top of the glass and then glass over them !!
There's a easy way that ends up stronger and there's a hard way that everyone thinks is good but its not as strong !!.
So what glass TYPE would you use to glass over you stringers with and how many layers ??

And the 1/2 H60 divinicell core would be bottom line for density ! If you using contoured make doubly sure all the individual blocks are sealed and fill between 100% every where!! this adds lots of extra strength and keep out any moisture !! I easier to lay it scrim side down and then you are able to fill the gaps easier and see what you are doing properly !