I'm not sure, but I think I have a plane covered with SIG plyspan. It is lighter than SGM silkspan.
I looked at the K&S website. They don't show any kind of silkspan. I had a full tube (10 or 15 sheets) of K&S heavy grade. Good stuff, but it's all gone now.
Having no more silkspan, I recently covered with polyspan. It's difficult to use because, sooner or later, you have to begin sanding on the clear dope. It's too easy to sand too much and into the polyspan. Once that happens, you are in for a fight trying to repair/smooth over the "fuzzies".
Floyd