Just took it on a 2-Day ride on the Katy Trail in Missouri. Check it out if you haven't been on this great trail and it is now linked to the Rock Island Trail. 267mi! After I figured out how to correctly tighten the straps, it was very secure and I hard noticed the pack behind me. I crammed a lot in there and didn't even max it out for a two day non-camping trip. There was no rain, but I felt comfortable with the quality of the material that my stuff would stay dry. I plan to add the front pack for a longer ride in the fall.
I tried several bags for an upcoming trip to carry rain gear and sneakers and this was the only bag that could do it with its minimal footprint. The buckle is big but the arrangement of the bag was such that I forgot I was wearing it.