I took some scraps and used a heat to see which direction seemed to shrink more. You can also make a little test frame and shrink it. I don't remember whether the grain goes accross the sheet or lengthwise.

I covered a whole biplane with Coverite one time and when the plane was already painted I noticed that on one of the bottom wings the fabric between the ribs was sunk in. Looked kind of weird to have the fabric straight accross on 3 wings and sunk in on one.

Jim