I honestly cant tell you how much material to use over the outside, but i can tell you to add an extra layer to allow finishing. you can easily sand through an entire layer while finishing. once the last layer is on, keep brushing a thin coat of epoxy at each "b" stage until the last weave is completely filled before sanding. filling the weave completely will not really add weight as most will be sanded off, but it will keep you from sanding into the glass too much. be sure to grind into your origional hull at the overlap at a very long taper to glass onto and to aid in finishing the seam.