First thing i would do is call or email David at CGW and ask him to explain things further. I am sure he would be glad to help, he always has any time i have needed his assistance.
I am sorry i cannot answer your question but have you considered changing the front sight as well. If you were able to remove the rear sight the hard part is done. The front sights are a snap to replace. It might just be easier to buy a matching front Dawson for the rear you already have, then they will work together.
Regulated pertains to a set of sights that are designed or calibrated to the pistol in witch they are to be installed. In other words they will be sized correctly to shoot point of aim on a specific pistol. In your case the Dawson rear sight is regulated to work with a specific Dawson front sight for a CZ 97, but the Dawson rear sight you obtained is not regulated for the stock CZ97 FO front sight. A single sight front or back cannot be regulated by its self. To regulate a sight one needs to know what front or rear sight it is to be regulated to work with and on what pistol.