My favorite is the Leupold line of scopes, esp the VXII 2X7X32.
I mount them on the Ultra base with LO PRW Leupold rings.
Here is a shot at the clearances:
Here is one mounted on my 20 USH:
Here is another mounted on my 12 USH. This is a old shot when I had the 4x4 rings and std pallet wood still on it.
Here is another combo that works well. Weaver 4x4 rings in the extension version.
I have one of these Nikon scopes. But its a varmint version. It is nice and clear and I have had no problems with it. I think you will like it!!
CW