I have to use a 20lb OEM hammer spring to get 100% ignition from my steel 75 kadet from all types of ammo. Below that and you start playing the game of which ammo/batch is better (in my testing CCI minimags and... of all things, Remington golden bullets work the best with sub-20 sprigns)
You might investigate the Cajun Gun Works extended kadet firing pin, which, like when you use an extended FP in 9mm, allow you to drop the spring weight.
But you must be aware an extended FP in a kadet WILL DAMAGE YOUR GUN if you dryfire it (supposedly even with snap caps).
How much your single action trigger is affected by the hammer spring weight depends on how much the hammer is cammed back by the sear as you pull the trigger. I suspect if you had a cajun/custom hammer/sear which minimized this, you'd feel much less weight difference.
Also, keep that FP channel super clean. You can also in theory mess with the firing pin return spring weight, but that risks your firing pin retaining plate flying off while shooting.
For me, I just deal with the full hammer weight, but I'm not particularly fond of sub 2lb hair triggers on my pistols anyway.
There are other things you can do to lighten a CZ trigger:
reduced power trigger bar spring
reduced power trigger return spring
a SA flat trigger
hammer/sear job or cajun drop in parts
polishing of all friction surfaces such as the trigger bar and the parts of the frame it rubs against
delete FPB lifter arm as the kadet kit does not have a FPB
