Sounds like a cool project.

Is there a reason why you didn't include the VX-3 1.75-6X32? I just bought one and also a VX-3 2.5-8x36. I have not mounted either of them yet but they seem like great scopes. Personally I would choose the 1.75-6x32 for this rifle. I bet you could mount it as low as any 20mm objective scope and it would give you a little more magnification for longer shots that may come up as well as more light gathering ability.

The 1.75-6x32 on good QD mounts would be great on this rifle in my mind.

500 grs mentioned not scoping this rifle. I also really like purpose built unscoped big bores. It really would depend on what I wanted to use the rifle for whther I scoped it or not.