The SQR is dreadful with a saddle bag, especially if you carry very much weight. The QR bagman is much better but still not perfect because the strap that would go around the seatpost doesn't work on the frame of the rack, so the bag can move, especially if you ever get out of the saddle. But with a light weight and a full bag (ie a change of clothes and stuff) it is pretty good.
The SQR is dreadful with a saddle bag, especially if you carry very much weight. The QR bagman is much better but still not perfect because the strap that would go around the seatpost doesn't work on the frame of the rack, so the bag can move, especially if you ever get out of the saddle. But with a light weight and a full bag (ie a change of clothes and stuff) it is pretty good.