Sounds to me like a poor match of bullet weight and powder... Sorry checked their site the 6.2 is max. You're supposed to reduce 10% and work up to what works best for you, not exceeding the 6.2 or when you have other signs that pressures are getting too high.
And your CZ won't take ammo loaded to commercial spec? Sounds like you have other issues to sort out.
FWIW I'd still consider finding another recipe that might be better for you rather than trying to make that one work by screwing with OAL... That can SERIOUSLY affect pressures, as can screwing with quantity. First and foremost be SAFE, its not worth saving $20 if leaves you crippled, blind or dead.