Holes in the backing of your grand should be no big deal at all. Get a
glovers needle, some thread, and stich away. if you need to patch an area, anytype of medium weight
muslin should do the trick nicely. The
Cyc is another matter all together. The big issue with both cycs and scrims is Puckers. The ban of the stitchers world. The absolute best way to repair a hole in a
cyc is to find someone, a seamstress, who knows how to darn. You might have heard of "Darning Socks" this doesn't mean yelling curses at them, it actually referes to a process of repairing holes by essentially re-knitting the threads. The advantage of darning holes is that it leaves next to no noticable marks. sewing a patch from behind or simply
whip stitching a tear will leave tattletales on the front side of the
curtains.
If you have no other choice, use an extremely small
gauge glovers needle, or curved sewing needle, and from the back side of the curtain, using as fine a thread as possible
whip the hole closed. try to work your stitches so they don't actually go all the way through to the front side of the
cyc. If the stitches do go all the way through, then attempt to get as close as possible to the previous stitch with your next stitch, Basically try to do your best to darn the thing. it takes time and patience but the longer you take to repair it, the better the results will be and the happier your lighting guys will be. And we all know it's all about keping the LD happy !