The entrances to single rider lines in comparison to where the standby is located vary from ride to ride. Logically there should be no reason why you couldn't go through single rider and use rider swap since single rider IS standby - just for a party of one. The issue will be whether there is someone at the entrance to a single rider line who can process the swap. If not, I'd get the swap passes added to the bands at the main standby queue entrance and then ask if you can head over to the single rider line after the issue the swap passes. I have a hard time imagining someone saying "no" to this since it's actually beneficial to both you and the overall efficiency of the queue.