With a magnified scope you will not be doing a co-witness setup, that is generally used with zero magnification red dot scopes. You could mount a scope on a carry handle but most find that's too high.

With a Mark III you may want a riser to elevate the scope off the flat top. I haven't added one to mine yet, but a little more elevation off the flat top would be nice.

Here is what the scope you are referring to, looks like. It's called the Ultimate One Sight System.






On the rifle: