I also like peep sights and have them on most of my lever guns. However, my Simson -Suhl .405 double rifle has express sights, a Talley QD scope, and, a peep.
You can see the express sights forward of the rear rib which has grooves for the Tally QD scope mount. As luck had it, the Talley QD peep also works and fits perfectly.
When I first tried the peep from a bench rest at 100 yards, the 300 grain Hornady bullet cut the edge of the one inch center of the target.
With this less than one inch group 4 shot regulation at 50 yards, I quit tinkering with the rifle and just went hunting!