Thanks Bernie, but I have an OMM Sherpa, and two Axiom racks. I'm certainly NOT going to substitute anything for the Sherpa, and the other racks are great as well. So, I need something that can hop from rack to rack.

I borrowed that very trunk bag you have in the photo one ride, and it rattled like crazy, even velcro'd down as tight as I could get it. It was all the plastic Topeak specific quick mount stuff that had nowhere to go on my rack.