Quoted from ShinyBall:1 bolt per unit. I want the back-up.
Maybe in your case you could rig up a secondary non damaging back-up like a bungee cord.
If you're going to half-ass it at least half-ass it right.
Do the opposing corner holes and use TWO bolts so you don't tear off one hinge side.
Oh wait, but then you might as well take the extra 30 seconds to put the other two in as well, because you've already spent 15 seconds doing the second one.