What I have done in the past is to tie or lash the coaming to the forward and backrest beams (or frames) and wrap the entire frame including the coaming. Use tape or cord to tie around the coaming like a spray skirt bungee, and cut a small hole in the middle of the coaming. When you are at the water for the test paddle, force your way through the small opening. This will keep water out well enough for the length of time you'll be able to paddle with the saran wrap skin.

I like the idea to use clear vinyl. It will work much better than saran wrap (I've not been able to paddle more than a few minutes with the saran wrap) and give you drastically better ability to evaluate performance over one or more paddles. It will be more expensive, but you can use the vinyl skin for a while before it will need replacement.

: Just about have the frame done on my new design. Want to try the saran wrap
: test for the first time. What do you do around the cockpit area? I have
: seen photos but never paid any attention to this detail. I am am sort of
: stumped as to what to do there other than just wrap it and cut out a
: hole??