Top Flite says that Monokote opaques weight 1.8 ounces per square yard.

The industry standard for glassing is to use the same weight in resin that your cloth weighs.... i.e., 1 ounce of cloth=1 ounce of resin.

So if you use .75 oz. cloth, you'll end up at a glassed weight, before primer and paint, of 1.5 oz per quare yard. I don't think there's' any way to glass a plane lighter than Monokote, but you CAN do it without a LARGE gain in weight, and add some strength and beauty at the same time... (no wrinkles!)

My non-commercial web site (below) has a lot of tips on glassing, including plug and mold making. Just go to the "Design and Building Tips" page.

Good luck!