I can't recall where I've seen the mod, but instead of a single cord on each side, why not 2-3 cords plus linelocs, set up like web straps. Light, simple, fine-tunable compression control.
OTOH, I find most compression straps useless for compression. My pack volume is relatively constant – full. As I eat food, my sleeping bag expands to fill the space. The best side straps are the ones I can hang gear from, one on each side.