First I was going to buy a bolt rifle for my wife but think again I want to buy a complete upper from stage Model 6H. So that she can swap the upper 16" and 20" whenever she wants. But now I'm running into a problem buy mount for a flatform upper. I scope will be a Nikon 3-12x42 M223, how high of the scope mount do I need or what type of scope mount I need. Please help me out, I would really appreciate it.