Sounds like it is growing a bit too fast and was likely hopped up ( pushed ) excessivly by fertilizer when you got it giving a taller tree with a thinner trunk. No.. staking that way would not work but with rope and tree ties and a tall step ladder you probably could upright it easily ...it sounds like it might break in a strong storm with rain and alot of wind so that is what i would do ...others may have other ideas...david

It's almost never too late to stake a tree under 3 inches diameter. There are a lot of ways to stabilize. You would be surprised what some simple staking will do. Doesn't take much effort. As long as you stabilize from two opposite directions, you don't have to go up more than 3 to 5 feet, even for a 15+ foot tree. Get some strong stakes or 1 1/2" pressure treated lumber/strapping, some strong rope, wire or cable, some old hose pieces for cushions and a couple of sticks for tourniquets. You might have to adjust, re-stake, pull and tug over time, but unless the base of the tree and roots are stabilized, you will loose it. Act now before the top gets too leaf heavy and unmanageable.
Greg

Thanks all for the tips. I ended up getting some stakes to stabilize them all. The interesting thing is that the red sunset maple was not leaning until about 8 feet up - then just the leader was leaning over.

Anyway, they are all upright now, hopefully this will hold OK until they get a little stronger. I did not think that I put down too much fertilizer, but I guess I will watch it from now on.