I seen a guy on a HD a few years ago who had them sitting straight up with the bottom of the bag on the right side passenger floor board and bungy cords to his passenger back rest. Looked strange but it worked for him.
2011 Cross Roads Sunset Red
OEM short windshield, passenger backrest, crash bars, saddle bag bars, heated grips, vinyl closeouts, tachometer, ambient temp, LED headlight, luggage rack. WD lay down licence plate.