Well Don, you already know how I feel about Polyspan from my e-mail, but for the sake of others, here goes. I love it! I was a die-hard Koverall or silkspan user. When I built the prototype for Aerodrome R/C's 57" Albatros C.III, K. Bengtson at Aerodrome persuaded me to give it a try. I was a bit hesitant trying a covering material I had never tried before on a model that I really wanted to turn out nice, but I went ahead and tried it. I was hooked from the very first minute. It goes on very easily. There is no adhesive on the covering itself. I used Sig Stix-it brushed on to the framework to ahere it, and then used a Coverite Trim Iron to attach the covering. I like using the trim iron because it gives me more control. I then used a heat gun to shrink the covering. It's worth noting that the C.III model has an undercambered airfoil. The model is 4 years old now, and the covering has shown absolutely no sign of lifting off from the undercamber. It has stayed drum tight, even under the hot summer sun. After shrinking, I apply 3 coats of nitrate dope, thinned with 25% thinner. After that, I use colour butyrate dope for finish, but any paint that sticks to nitrate dope would work fine.

Even on compound curves and wingtips I have never had a problem and wind up with wrinkle free covering. The secret here is to dig out the bigger covering iron, and then heat and stretch the covering as you pull it down around the curves. If you just try and mash the covering down into the wood, you will get wrinkles. Also be careful when shrinking. It is possible to over-shrink polyspan, and you will wind up with a hole where the covering has pulled itself apart. This only happens if you hold the heat gun in one place for way, way too long. If you shrink the Polyspan with an iron instead of a heat gun, you will avoid this problem entirely.
If you do get a hole, I have found that the best patch is a piece of silkspan. Tear a patch of silkspan the size you need (tearing will leave a softer edge than cutting, allowing it to be blended into the covering for an invisible patch), and spray it lightly with water and then dope it on. Sand the patch lightly, apply more dope, sand lightly, apply more dope, and sand lightly again. You now have an invisible patch.
Two areas you need to be careful with when using Polyspan.
a) Make sure you apply it so that the slightly shiny side is up! This is very important, because if you get the wrong side up, you will get a horrible case of the "Fuzzies" that will not go away, no matter how much dope you try and use.

b) DO NOT SAND HEAVILY BETWEEN COATS OF DOPE! At the absolute most, you may give the covering a very light once over with 600 grit after the 2nd coat of dope. If you sand into the polyester fibers, you will once again raise fuzzies that no further amount of sanding or doping will eliminate. Your only option is to strip off the covering, or lay on a piece of silkspan over top of the fuzzy area.

Polyspan is super strong, very puncture resistant, and holds its shrink. I have use it on my 57" Albatros C.III, 47" Fokker Dr.1, 50" Noorduyn Norseman, 41" Sopwith Snipe, and 78" Gotha G.IV. All 5 models look as good as the day they were covered. Not one has shown any sign of loose or sagging covering, and not one has a wrinkle. The finaltexture of Polyspan is hard to describe. It is not glass smooth like a plastic iron on, nor is it textured like a fabric. But it does have a slight texture to it that give the model a more realistic look (for a rag covered airplane, anyway).

I love it so much, I even made a video of how to apply it. When building the Snipe, I video taped myself covering the airplane, right up to the painting stage. Aerodrome R/C sells the DVD. I warn anybody thinking of buying it that it is hardly a professional production; just me, the Snipe, polyspan, dope, and occasionally my daughter's cat. But if you want to see how to apply it, I think (Hope!) it gets the point across.