Originally Posted by AviatorJ
Just hold the gun perpendicular to the direction you're driving the rivet.
This. I don't recall setting those rivets to be particularly difficult (admittedly it's been awhile). The key, even with a swivel flush set, is to get the gun in a good, comfortable position relative to the surface so that it doesn't walk when you press the trigger.
Oh and I didn't back rivet squat beyond the control surfaces where back riveting was specifically called out in the plans and my riveting turned out just fine. IOW back riveting is "a" way but not "the" way.