A post duplex is a good one, and I have run a few. IIRC, the distance between the center and the lower post may be greater than a standard duplex. I believe I compared it before in 6x and/or 2-7x. Why does that matter? In my experience, I often had a POA/POI at 200 yds and used a standard duplex as a POA/POI at 400 yds, by using the lower post juncture. That worked out with a plain duplex. It might not matter to others.
I always said, as to simply 'holding over with any scope' you could hold on the back of a deer at 300, and about a foot over at 400 (with many modern High Vel rounds)........no doubt better to use a reference point as a POA where you want the POI.
