Mike- a friend of mine also uses a modified hole saw. He purchased 2 the same size, and ground most of the set off the outside of one hole saw and modified the other as you did, making it sharp.
First he cut through 2 thicknesses of 1/2" spruce plywood of good quality with the hole saw to make the template for holding the patches - alignment pins are installed in one board's corners and clearance holes in the the other.

Then, separating the boards, he puts anywhere up to 50 or 100 layers of cloth, then aligns the pins/boards. He then puts a couple clamps on the boards, then runs the sharpened hole saw down through the holes, cutting 50 to 100 patches perfectly, loosens the clamps, moves the cloth, re-clamps drills, etc. It takes me longer to type this out, than for him to cut 300 to 500 patches.