You only replaced the hammer spring with the 13# spring and did not replace the firing pin spring and the firing block plunger spring? No misfires?
That is correct.
In first handgun I replaced firing pin as well, because I wasn't sure and few people told me to do so.
But for the next one I didn't touch firing pin. I found few posts (there is thread about it, somewhere on this Forum as well) with info that you have to play with firing pin, whenever you go with mainspring #11.5 or lower.
However in both I replaced plunger's spring with "RP-FPBS Reduced Power Plunger Spring". I've just checked the invoices form CGW
I wrote that mainspring would be enough for start... and that seems to be true. I use my CZs mostly for dry firing practice, but I can feel that the handgun with all parts replaced has gotten a little better trigger pull (lighter and smoother).
And no misfires. But I shoot branded ammo only.