I just realized that I do have a Czech pistol after all. Just like you it is a CZ-52.
My late Brother had a 9mm barrel for his and did some interesting experiments with heavy 9mm bullets loaded long which left more powder space. That was with the original 7.65 magazines. He also had a couple of mags which were blocked off to feed the 9mm better. Of course then they would not hold the 30 caliber shells.
You might want to check the laws about converting them. Someone told me that doing that can violate the C&R laws in some instances.