Another benefit of compatibility with the Talley QR system is the Talley Peep Sight. Here is a pic of my Hynden/Simson .405 double rifle with the Talley peep installed:

The height above the rib is just right to see through the V of the express sight, so the peep was immediately useable without adjustment.
Link to Talley site: http://www.talleymanufacturing.com/Products/Scope-Ring-Bases-Peep-Sight/Peep-Sight.aspx

First shot at 100 yards went into the bulls eye.:


If you are interested, I can provide more information.

NRA Patron, TSRA, Whittington Center, DWWC,DRSS
Reloading Ballistics App at http://www.xplat.net/