The boat I'm working on right now, that is destined for a mudmotor, has a layer of 6oz glass, then a layer of 5oz kelar and lastly another layer of 6oz glass. I'm not sure how well dynel sands but if its anything like kevlar it takes a little work and the last layer of glass to get smooth transistions. The idea behind it is probably overkill since I've been running a mudmotor on my wood boat for 3.5 years with little to no problems to the hull, but I figured peace of mind is great.
Brad