Take a look at Rickk's 170 rebuild thread. He recently glassed his deck, which is plascore (similar to nidacore). He used a vacuum bagging system on his.
I will be doing my floor in the not-too-distant future. I am using nidacore (3/4"), and will be adding 2 layers of 1708 on both sides (as recommended by Eugene/Shipoke), and a layer of 3/4 oz mat on top (to minimize fairing). I'm not planning on vacuum bagging. I have glassed some nidacore bulkheads without a vacuum and they seem to come out fine. Wet out the scrim on the nida core panel, lay on the 1708, and wet out the cloth. If you're addiing a second layer, you will get a better bond if you add it before the first layer cures. Some people orient the second layer different from the first to improve strength. I'm not sure if it is at 45 or 90 degrees or what. I'll need to figure that out before too long.
Oh, and make sure you have a flat surface to work on. The nidacore is pretty flexible in its raw form, but is very rigid after being glassed. It will take the shape of whatever surface you have it laying on.
Good luck, and take pictures!
