Redfield used to make a series of scope bases that had an attached 'flip-up' peep. i found several of these bases at a sporting goods store cleaning out the old junk.
Mounted on the back of Leupold Weaver style bases, they make for a great iron sight backup system on rifles with QD scopes. i have installed one on a Kimber 300 WSM, installing a front barrel sight (NECG). Also on a custom Mauser in 338-06, again using the Leupold Weaver style bases and Leupold Weaver style QD rings. they work great!
the key for me has been the Leupold Weaver style bases.. they are steel (better for drilling and tapping in the screws needed to hold the Redfield peep on), and are lower than many other makes. this keeps the peep as low as posible, reducing the height of the front sight.
