I have a burris fastfire mounted on top of a burris shortmag 3-9 on a scope accessory rail. I have it mounted vertically and inline with the scope (as opposed to canted or mounted to the side of the scope). I like it better that way, but there are a couple of drawbacks. First, a different cheek weld is required because the red dot is on top of the scope, but there is no real waty to get around that one. Second, it wouldn't work on a scope with large turrents, and third, because its on a short scope it only fits in one spot and there is no way to adjust eye relief of the red dot (scope rings are in the way). I haven't been able to get a proper zero with the red dot yet, but i haven't had much time to play with it either...a seperate red dot on a quick release mount would work better, but then you would obviously lose the versatility, and its the versatility I like. Cheers