John, I am not familiar with covering over poly span with a clear Mylar. What is the purpose of doing so? Is it a short cut to avoid sealing the polyspan? Is it and iron on heat shrink material. I am in the process of covering my vintage Monogram Piper Cub Special and have applied the first coat of dope to bare wood. I dope in the garage or outside on nice days. Yesterday was in the sixties and clear, today it is drizzly and cloudy so progress is slow. I thought about covering with silkspan but decided on polyspan. Richard