RE: EOTech Issue on AR
You're going to want to pay the bucks and buy a high mount riser, if not for a clear sight picture, but for head position and shootability..
I tried going cheap a few weeks ago and mounted a a spare 3x9x40 scope on my A3 using tall Weaver rings, under magnification, the front sight tower was only a shadow, but the scope was just way to low to shoot comfortably.
You might want to try Badger Ordinace as well, I'm pretty sure they make a ring for mounting the eotech, but once again, they are expensive.