TOPIC: what oz. fiberglass cloth for core?

I was looking over all the choices for glass material...well, what a headache! Anyhow, it seems like biaxial cloth may be the way to go. The plan is to put a layer down first before I glass in the new core. I'm guessing this layer could be just chopped mat or something not very thick. Any ideas of what I should use for that first layer and then the "topping" for the core?

Starting from the outside and laminating in: gelcoat, veiling mat, 1 or 1.5 oz mat (sure you can use 2 also) then the structural plies I personally like vectorply but there are many variants. I like to use at least 2 thicknesses of vectorply and if extra thickness is needed use mat layers between. If you have rolled it nicely, the vectorply leaves a beautiful finish, but my buddy puts on 1 or 2 layers of mat for a more conventional look. And you can gelcoat it again to give depth of color.

You can use 22 or 24 oz roving if the price of vectorply seems steep.

Now, if by core you are meaning balsa or foam, then use 1 layer of vectorply or roving instead of 2, then use mat, then do your core, then use mat to finish.
Hope that helps.