In the past I have alternated between mat and either woven roving or cloth when laying up fiberglass. I read recently that if you are using epoxy which I am (West) you don't need to alternate because the layers adhere so much better than polyester resin. I purchased Mat, woven roving, and cloth just in case because it is a good hour from the nearest source from where I live. The hull is about a half inch thick so I anticipate about fifteen layers of glass. The diameter of the repair is seven inches. Advice from those who have been there will be appreciated.