If you put your dot/reflex sight above your scope, there is a huge distance between your bore and the sight. Especially at short distances - for witch you want to use that dot - this is bad. You'll have to compensate a lot for different distances, thus loosing the all the benefit of quick transitions with your dot sight.
The 45° mounts do look akward, and at first I had huge reservations, but after picking up a m4 of a friend with such a set up, I became a believer. I needed verry little training to get used to this set-up as shooting at the angle does feel quite natural, despite how it looks. Most 45° mounts are so constructed that you only have to turn your rifle to get a sight picture thru the dot. No head movement is needed. scope-dot-scope transitions are a breeze and feel quite natural, and fast!
mounting my 15-22 is just as fast, if not faster because of the faster target aquisition with the dot sight- at 45° as straight.
