Tim;
If you don't know, a Bar Tack Machine sews the really tight short line of sewing used on most outdoor gear. It makes the sewing strip in a second or two. The guy who has worked on my bags (and built some of the sail cloth rigs for my lighting gear) converted the domkes in about 15 minutes each. It's really simple work and cost little. I bought my hardware from him.
So, you know what I'm talking about..
http://whafi.com/sewing-techniques/how-to-sew-a-bar-tack
On the adjustable end of the closure, be sure to fold-over a short amount of strap and double bar tack, so the strap can't work loose from the hardware. Mine have lasted and worked well for years. I can open and close them easily with gloves on in winter, with one hand.
I never scratched a lens but, saw it could easily happen when working fast or when tired and packing up.
pkr