I have another thought on the Magpul grip that I wanted to throw out there. It's just pointing another possibility that hasn't been brought up before. With all the complaints about the Magpul grip being out of spec and needing special fitting to make it work, have any of those with problems ever tried other brands of grips and did they fit without modification? If the other brands fit then maybe the complaints are justified. But what if it the CZ frame that is out of specs? That is a possibility.
The CZ frame isn't machines to spec, it's molded, and it's entirely possible that the molding process might have left some flashing or high points that are responsible for the grip not fitting. It's also possible that the original CZ grip just has wider tolerances so that it fits while the Magpul grip might have tighter tolerances so that it's harder to fit. It's also possible that when the original CZ grip is installed, it is fit by using a little "persuasion" by the use of a big hammer to force it on.
I'm just saying that it takes two to tango, and if either of the two are out of specs, then problems can happen and it's hard to tell which one is actually the one out of spec. It might be the Magpul grip or it might be something else. We are all going on the assumption that the CZ frame is perfect and we forget that it too has specs that might not be 100%