I was faced with the dilemma of being able to see at distance well but the sights were so blurry I didn't shoot my doubles for several years as a result. Eventually I had JJ Perodeau install a Docter Optic 3.5 MOA Red Dot sight on my Evans 470. I was very hesitant to do it but now wish I had done it earlier.

The sight attaches through slots milled in the existing sight base so if I want to take off the optical sight I just unscrew it and I have the original iron sight ready to go. The optical sight unscrews using the rim of a 470 cartridge, very clever.

This picture shows the milled slots in the qtr rib for the optical sight. If you didn't know they were there you wouldn't notice them.

On my Holland Royal 500/450 I had him make a new sight base that replaces the iron sight since I didn't want to mill on the Holland due to it's value. I lose a little bit in practicality since I would have to drift out the sight base and replace it if I want to use the iron sights but it seemed a reasonable compromise to retain the rifle's originality.