Hey MinnFlyer,
I did go over it with an iron to finally nail it down after I got tired of returning to the shop to reshrink. I was not real happy with the finish though, and even still the problem persisted to some degree. I didnt use any surface treatment on the balsa however, as I had not originally planned on fastening it over the entire surface.

Just to clarify, I did stretch the covering tightly in all directions when applying the film and was pretty tight and had no wrinkles before the final shrink. It was not 'drum' tight but was as good as I could get it by hand. The technique I used was out of one of those expert "How To" books commonly found in the back of MAN.

I like rusirius suggestion of working in a very warm shop. I will be conscious of that in the future.

Anybody with other thoughts?