I've been mounting mine underneath. Maybe that's why I keep shooting high.
This really doesn't surprise me, coming from somebody who cries because of a papercut.
i just bought a eotech, i tried mounting it as far back as possible near my mbus, but im sure its designed to be at the edge of the receiver toward the muzzle end, work better for me that way. i guess its just personal preference, seen them used both ways. aimpoints like the micro, i always seen them mounted toward the muzzle end of the receiver, and some even further down on the handguards of ak's & M1A's. i guess it depends on whatever fits your fancy..
It's really a matter of personal preference and what works best with your shooting technique.
Farther forward will give you the best field-of-view.
Farther rearward will allow you to hold your dot steadier on target.
I put my old Aimpoint C3 in a LaRue cantilever mount as far forward on the receiver as I could-- same with my current H1.
C3
H1
^^ This, in an actual shooting situation you don't want to loose your field of vision, you don't have time to be spending all day trying to acquire new targets through your sight.