I recently picked up a Large Saddlesack off the list (thanks Captain Conway!) and needed a rear support rack for it. I had cut up some older racks to harvest the struts and make my own "Pec Dec" inspired by Ron of Rons Bikes. This one uses two sets of struts that are nano strapped to the bottom leather panel on the bag. It provides more than enough support and was much cheaper than an R10.
On another note, I've been through numerous saddlebags since the last time I owned a large saddlesack circa 2014 and I have to say, its still the best user-friendly saddlebag I've ever used. This is the first bike that I've used one on that has a kickstand, so loading/unloading is a bit simpler than in the past. But still, kudos to Riv for coming up with this design, it's a pleasure to use.