TOUGH PROBLEM!
I have tried twice to cut feet off nylon tights. First time I just cut them, and they ripped upwards. The next time I tried to sew elastic horizontally around the ankle and cut the tights just below the elastic. ThenI folded the lower edge up ove the inside of the elastic, to keep the nylon between the elastic and the leg.
It would have worked except for two problems: The elastic was too tight, and, I hand-sewed the elatic with separate stitches about 1/8 inch between each stitch (I you use a chain-stitch, the elastic won't work).
The individual stitches each had a knot, though small, which would irritate my skin.
So I don't know what more to suggest. And your material sounds a lot worse to deal with than nylon.
Good Luck!!
anonymous[/i]