There's a gent in Alaska who built a 450 #2 DR on a Huglu 12g SXS. The rifle has been shot a bunch with stout loads and is way loose. Couldn't tell if the bar stretched or the hinge pin bent. Since the CZ is a Huglu, thought this might be appropriate input. Building a DR on a SXS shotgun is so much work, it's kinda dumb to start with a questionable action. I built my 450 NE on a J.P.Sauer 16g BLE and it's tight as can be after 300+ shots.
Otto