yes, exactly, I use the SQR. It's very nice for easily taking the bag off and on. I don't keep my bike indoors so leaving the bag mounted is not a practical option. Got to say though, it is a bit heavy. Fits in with the general pattern on this bike!
These days I have freed up that tree and now I am hanging the bike in the car port, out of the rain. It's a better option I think. We just moved into this apartment a year ago or so and are still figuring out the details!