With a 56mm Objective we recommend going with the High (1.25") mounts.
Yes, we recommend at least a set of 1.5" extra high rings.
The Leupold Mark 5HD 5-25x56mm has a main tube diameter of 35mm and an objective lens with an outside diameter of 2.5". So you will need a set of 35mm diameter 1.25" high MDT Elite Scope Rings.
Typically you would use extra high rings with a 56mm objective lens, however, the way the Christensen Arms MPR's pic rail is set up, it gives you some extra height above the barrel. So in your case, I think using high rings would work. Try to measure the distance from the top of your barrel to the bottom of the picatinny just to be sure. Although I am fairly confident that the high rings will work just fine.
The MDT Elite Scope Rings that I recommend are the 34mm extra high rings in order to allow clearance for the 56mm objective lens. MPN:102718-BLK
You will need High to Extra high depending on the rifle barrel and mounting system, if you email us Techsales@opticsplanet.com with those details we can find the proper selection for you.
You would need high height rings.
You could get away with the mediums on that setup: 3JN-RR-ESRS-104100-BLK, of course those are on a 3-5 month backorder, so you might want the highs: 3JN-RR-ESRS-104101-BLK
With the 56mm objective you would want the Extra-high rings.
You would need these rings: 3JN-RR-ESRS-102718-BLK