Flex-Seal to mend shutter curtain?

I tried the black fabric paint tip on two shutters recently and can confirm it works quite well. I patched up a Zorki 5 with some pinholes and a Canon IId with a fair number of pinholes. Seems the rubberized curtains on the Canons do not age well. It will need new curtains at some point but this gets it working for a while.