A little background on SLC covering. As Lauri guessed, it is polyester with a fuel proof, heat seal adhesive on it. It's less than .001 thick, so if the edges are properly ironed down they will disappear. You can barely see the line and most people can't feel an edge less than .001 or .002in. thick. The film edge will get buried under primer and paint. I'd be more concerned about the polyspan edges showing through. The film is about 1oz/sq.yd.
Doug Moon used it on his Gieseke Nobler ARF's a few years ago. He and others put automotive paint and clear directly on the film with good success.
After six or seven years of leaving planes in the car for a week some of them have developed bubbles on flat balsa sheet sides. They can be ironed back down without hurting the paint.
The website, sadly out of date, has info or send me an email. home.earthlink.net/~philcartier
A 10-12ft sample is $6, prepaid. 100ft x 15.5in. roll is $35 plus $6 or USPS Priority mail and $1.25 for PayPal if you don't want to prepay by check or MO
I can't take credit cards at the moment. Visa screwed me out of a goodly sum on a processing error, so I'm looking for alternatives.