Unfortunately this bag did not stand up to normal use. The handle for carrying is on the zippered opening and the zipper broke on my first long trip. Do not recommend!
I use a rear seat bag as you do. I have found that the Kreiga system fits my needs real well and it's tough and waterproof. I have the US30 as the main bag and 2 US10's that can be "piggybacked" to it. The Kreiga comes with a multitude of straps for attachment to darn near any MC. I don't very often recommend products, but this is one that I'm totally on board with. Oh yeah, with this set up I can carry almost 2 weeks worth of "needs" in the Kreiga alone leaving the saddlebags for those things that stay with the bike at motels.