I have also had some polyspan clones.  Uneven texture, thin spots.  No way to ever fill that weave.  The original Starline was the best but are they in business anymore?

A similar product is Thermalspan.  Apply and shrink like polyspan but Thermalspan does not have the "grain" like polyspan.  Thermalspan is as strong in the chord-wise direction as span-wise.  The weave looks tighter.  Like polyspan, it needs to be installed with the proper side up.  I doubt if the company that made this product is still around.  Since fewer are building these days, and the demand for such items has dropped, no reason to produce it.