RB,
Sounds like it should do the trick. Another thing to look for is: Joann's here had 100% cotton 10 oz. unbleached bull denim on sale 50% off (I think Daryl mentioned bull denim as working well once, so I looked at it). I think they also have heavier, but it was either sold out or not 100% cotton that day. I think the 10oz. would measure in the neighborhood of 0.020", maybe just a little more. It seems to shoot pretty well after washing -- it was a little disappointing unwashed because it wouldn't take up enough lube (I spray it on before loading). I have had some "magically accurate" denim from Walmart, but as usual, when I ran low, I couldn't find anything like it in stock. The cotton duck I had tore also -- some of it shot well, other bit of the same bolt would tear all the way through (doughnut patches) with reasonably mild charges in my .40 and not shoot well in my .50 at all.
I like (actually prefer) square patches, too -- it is all I use for plinking and woods work. As long as the tip of the rod is not big enough to catch a corner when retracting the rod, square is as good as round and doesn't require anything special to make. Also, the precut round ones irritate me unless they are a little oversized -- too easy to get loaded cockeyed in a primitive setting if you get started the least bit off center! I found the ".50" cal. ones are better for my .40, for example.
