If you aren't afraid of cooking at 275 in your UDS, skip the foil, leave the thing closed, and just listen for the sizzling to die down. That means the stall is about over. Should take around 3.5 to 4.5 hours at 275 cooking temp, depending on meatiness of ribs.
People don't comment on this too much, but when you leave the foil in the kitchen and just cook straight up, you can listen to the meat cooking by keeping an ear close. Listen closely, you'll know exactly what's going on by the sizzling sound you hear.
Modded Brinkmann Gourmet. Basic UDS. Rescued 22.5" OTS. SJS Mini-WSM. Stubbs. B&B Oak Lump.
Cannondale 2009 F8 (for burning off all the great BBQ)