I popped out the mainspring retaining pin (which you also have to remove to swap backstraps) and swapped the mainspring with a CGW blue 13# hammer spring. I also swapped the trigger return spring with a CGW reduced power trigger return spring.
In stock form: DA >8#, half-cock > 8#, SA 4.5#.
CGW 13# hammer spring only: DA > 8#, half-cock no data, SA 4#.
CGW 13# hammer spring & CGW reduced power trigger return spring: DA 8#, half-cock 6.5#, SA 3.5#.
I tried swapping the horrible recurve trigger with an 85c trigger and couldn't figure out why the trigger pin wouldn't install... The pin is 2.5mm. All steel frame CZ's use a 2mm trigger pin and the 85c trigger pivot holes are 2mm also. I'll have to open up the holes. I'll use a thick 97 trigger.
The trigger return spring and trigger are able to be swapped without removing the sear cage or trigger bar, but it's more complicated and requires some extra finesse.
After dry firing with the new mainspring and trigger return spring, I'm happy where it's at. I have an extra CZ UB 0.0 disconnecter that I'll fit to the gun, and I'll add the 97 trigger too. Once I get night sights, I'll put those on and call it good. Maybe I'll buy the RC Tech spring kit or the MCarbo spring kit to see how the springs compare to CGW.
One interesting thing I noticed is that the internal parts are extremely smooth. They look nothing like steel 75 internal parts. I was planning on polishing the action, but it looks great as is.