Just joined the site after trying to find info about this topic. Found the site via rimfirecentral. I mostly shoot Savage rifles but have an itch for a 221fb CZ, (just put together a 20vt but didn't like having to clean the barrel so often).
Contacted Williams about a rear peep sight that might fit the 527. Haven't gotten their info yet by mail. Friday I spoke with a tech at CZ USA about adding a peep sight and he suggested mounting their Weaver rail ($60) onto the 527 and asking Williams if they made a sight to fit that, the FP adjustable.
I'm still scratching my head about this conversion. The Savage action is drilled and tapped for rings, so the Williams sights simply screw down on the rear of the action. Has anyone tried the Weaver rail on their CZ? The 221fb is a great caliber for 200 yrds, the peep sight would be a perfect fit.