I am sorry Mo, I misread you previous post and thought you were referring to piggybacking powder loads of Trail Boss and Red Dot powder. Dual loads or staged powder charges are usually not a good idea.
Piggybacking a red dot optic and a scope is completely doable, and actually works well.
Our 3 gun match shooters are required to make quick hits on targets out to 50 yards and long range shots out to 200yards using the same gun. They almost all use the setup like I showed in the picture, with the red dot set at an angle so that it is not terribly high above the bore.
They simply turn the rifle a bit sideways to acquire the dot and place it on the target, and they can do it very fast.
I am sorry Mo, I misread you previous post and though you were refereeing to a duplex load of Trail Boss and Red dot powders. Not usually a good idea.
Piggybacking a red dot optic on a scope is not only possible, it is often the answer to several problems.
Our "three gun" match shooters are required to hit close in targets rapidly and then transition to 200 yards instantly and with the same rifle. The normally use the red dot for the close fast work and the scope for long range precision.
My own setups work fine and I do not have either of them using the red dot way up in the air. they set to the side at an angle. We have mounts and rails available just for this style application.
http://www.shootingusa.com/SIGHTING_IN_S...i_gun.html
Boy did I mess up this post!!!!
I thought the first one did not take and redid it.