RE: What the heck am I doing wrong???????????
Sounds as though you are using Monocoat brand film since the backing material is clear plastic instead of the paper product used with Ultracoat.
This is an extra benny for you. Save the larger pieces of the clear backing material for a plan protector when building over plans it works wonderfully well in this application and interestingly enought Tower sells dedicated rolls of the stuff for the purposes but you get it for free.
John