I used the Morris method to skin two boats and each time it worked really well. I sewed the nylon dry, pulling just finger tight. I used a hose spray to shrink the boat after skinning, leaving it out in the sun for a couple of hours to shrink drum tight. When it was bone dry again I varnished it with Varathane (water based outdoor) and have never had any problems with loose skin, wrinkles etc. on the boats that is
I did the sewing in the basement at the end of the winter and shrank it on the first hot day so can't tell you whether the outdoor humidity has anything to do with the finish. I also used 12 oz nylon. You should use a thimble though for sewing as tiny blood drop stains are a pig to get out of white nylon.