It's the best idea I've ever had, if I may say so! I also use my commuter bike for overnight trips and recreational rides, so I don't always want the bulky trunk bag hanging off the rack. On an overnighter, when I get to a hotel, I can simply remove the quick-release Topeak bag and slip on the snap-in saddle bag, which has anything I might need for a typical repair and allows me to wander off into the woods or some other place where the trunk bag can get snagged or might slow me down. Long sentence, huh?