I would think Mertons is a great source for this info. I agree cloth will be stronger although a little tougher to work with. I have used biaxal for my last few projects and was pretty happy on all levels. I use Reinforced Plastics in Farmingdale. Ask for Craig (great guy).
I agree that mat is by far stonger. However it is much harder to work with. It appears that your house is constructed of Â¾ plywood. Therefore you already have given the vessel great strength. If it was my build I would therefore go with mat. Most likely two layers inside & out. The process will go faster and the look with some fairing compound will give a nice finish. Re-enforced Plastics is a good start. If you need a second opinion I would also talk to Warren at DynaGrout http://dynagroutfiberglass.com/default.aspx?pageId=1