We've been covering directly over foam the past year with Topflite Econocoat, Tower coat, and Toughlon (Sig's stuff which they no longer have). Toughlon can be ordered from AIRBORNE MODELS , Livermore, CA. The film Howard has(FLITECOAT) IS Solar film and it is great stuff, probably the best to use. I really like the Toughlon also because it is thicker, but has the lowest application temp.(136deg-250deg F)- wt.= .27oz. sq. ft. It is a little harder to go around compound curves, but we are building straight wings/tips w/ tapered T.E., so no problem. AirBorne also has "LightTex" which has even lower app. temp.(136deg. - 200deg F) It is lighter in wt. We've used it too and really like it. It is cheaper- They have the same big color/transparent selection Sig had, even checkerboard. Prices range for lightTex- 8.99 tranp./roll to 10.89 Opaq., Toughlon- 8.99 Trans/roll to 10.99 Opaq./roll, 12.99/roll-Checkerb./Pearlized. Roll size-31-1/2" x 2 meters. They have a nice website if you wanna check'em out.
Stay away from Ultracoat when applied directly over foam. It's temp. range is much higher. I believe it is even higher than Monocoat. I think is about 225 -230deg F to get the adhesive tacking and the shrink temp is about 280deg F up to 350deg F.
Overall the Airborne stuff is the most user friendly for foam/ also cheap.The Howard flitecoat which Howard sent me is also super easy to use over foam which is most likely Solarfilm which is higher in price than ECONOcoat, Towercoat, and the Airborne stuff.
Doug