You can use the nidacore as a form and heavily glass around it for the bulkheads, but it won't be adding any real strength which is why CW is suggesting the straight glass. Foam core would be a better option, or even good marine ply. To make the glass straight you can do the layup on your garage floor, put down a few layers of heavy plastic drop cloth, and make sure it is smooth. When done one side will be smoother and thats the one you face outward, the rougher side will be out of site when done.
To be honest I'm not a fan of woven roving, it's used to add bulk more then strenght. I'd rather go with several layers of biaxial 1708 to 2408, but thats just me.