I just ordered a 455 American in .22 WMR. What rings and scopes are you all running on your CZ's? I thought I saw somewhere that they have a high bolt throw and taller rings may be necessary.
I have a 452 (same receiver size) and I bought a set of Weaver rimfire rings at Walmart for $8.99, they gave good clearance with a Leupold VX-2 3x9 and a Nikon rimfire 3x9 which has a slightly larger eyepiece than the Leupold. In my experience I do not see bolt clearance as an issue.