Chris- Have not used Snow roof but I have built several kayaks, the first 3 were skinned with canvas and sealed with alkyd paint thinned with linseed oil. Canvas is nice to work with but it will rot especially if stored outside. Another drawback to canvas is that it is quite heavy after soaking up the 3 coats of paint, the skin on a 17' Aleut single weighs a good ten pounds. My last three boats have been skinned in 8oz nylon and it is a very good material, weighing half of what a canvas skin would weigh. I like skin boats because they are fun to build,the cheapest to build, weigh less than any other type when skinned with a synthetic material and using a light weight wood for most of the frame.

My last boat an Aleut single weighs 30lbs. (It's for sale by the way)