I have a Topeak tourguide bag, and I had the same problem especially when I tried to ride with my amfib mittens in winter. Not enough space between the interrupter levers and the back of the bag. My wife was throwing out a 1/2" thick plastic cutting board so I cut a piece large enough to extend the bag 1/2" further out from the mount, drilled the appropriate holes, mounted it between the mount and the bag, and my thick mitten/gloves reach the interrupters perfectly now. I didn't have to tip the levers down, but they were down a little from horizontal anyway.