I buy it from Aircraft Spruce. I also buy the dope from their as well. The fabric is the uncertified lite used for ultra lights. I believe it is 1.7oz per yd but it takes fewer coats of dope to fill the weave. I actually use Minwax Polycrylic ( water based) to fill the weave. I then add the stitching and tapes then a few more coats of Polycrylic then sand and primer and paint.

I have used Sig Koverall on several builds and I prefer this fabric.
Later!!
Anthony