Figured this out (mostly) if anyone else happens upon this.
Set AM's Window Mode to Window in the General Options. Then drag the window to the other monitor, position it how you like (don't maximize, sadly), and close it. Next time you open it, it will be in that same spot. Only works if you use the Window or Window (No Border) modes, but no border was good enough for my purposes.
Most Windows programs work like this, I just forgot AM had a windowed mode.
