Try a long two point sling... That's what I plan to do. Both sling attachment points (can't really call them swivels if they don't swivel, right?) will be on the left side of the rifle so if I leave the sling long (for now it's an M14 rag sling) I should be able to make it work.
FWIW I'm not a fan of most tactical slings... In my experience with a couple kinds, they're usually made for comfortable carry for long periods, or for quick access. They don't work very well as true shooting slings IMHO, they move around too much. And if you have a PRS stock on your rifle, you're more interested in accuracy than being tacticool, right?