I depends on exactly how high over the bore the scope is compared to the sights... You do mean that the red dot is higher than the post, right? Just how far "off" is the dot?
The fancy AR15.com word is "co-witnessing" the sights. Aimpoints, Trijicons, and a couple of others designed for the AR have flat-top bases that put them at just the right height that, when looking through the rear peep, the red dot will be sitting on top of the front post.
I have a Tasco PDP3, mounted with the regular rings on a Bushmaster scope riser... 2 rings in rear, none in front, so the scope hangs out over the handguard. Now that I know my irons are "on", I can keep a check on the tasco to make sure the red dot stays on top of the front post.
I prefer mine to be a tad higher than that, so that the red dot is in the center of the glass when I'm looking OVER the rear sight. This will put it a half inch above the post when looking through the peep. Otherwise, the red dot is kinda high in the glass and it just doesn't look right to me. This was much less of an issue when I had a flip-up rear (ARMS #40) but I have a fixed rear now (DPMS) so it's a bit different. I kinda wish I still had that ARMS.
