6 layers of 6 oz or equivalent.

I use my 4 oz that I used for building and would put one complete sheet over the mold. Then I always have a box of scraps (all weights) and I start using all of that up, overlapping areas and reinforcing others. Then I usually add two complete coverings of the 4 oz again. I mix some graphite in to make it black. It takes several days for the seat to get rock hard. For a few days it's hard but bendable but a few more days and it will get really stiff. But get it off the mold.

When I first started doing these I used to use fiberglass roving. I would do a layer or two of 4 oz, a layer of roving and then two more of cloth. but I think you just eat up more resin and roving is not easy to bend it around everywhere.