I usually build S&G kayaks which makes little differnce in the layup, and I use 4 oz glass, which also makes little difference overall, but I use 2 layers over the entire hull with one to two layers additional at the pointed parts of the bow and stern, the sharper the point the more glass is my rule of thumb.

Using 6oz, i would use one layer outside for a "light" layup, two for heavy. Add one layer 4-6" wide and a two to three feet long along the bow and stern from a few inches above the waterline back along the keel, add another layer say 4"wide by one foot long in the area where the bow (and stern) stem meet the keel where it will most likely encounter hard things.

Cut the additional strips on the "bias" so the 'glass will lay down easily.

--eric