If someone with access to both PAL and NTSC 7800s wants to buy one and give their feedback, feel free to share their findings. But I would not recommend anybody in PAL land be the guinea pig unless they have access to play on an NTSC system. Maybe someone can run the ROM in Prosystem emulator under PAL mode and give feeback...
The original NTSC centipede works on PAL systems very well. Only the bottom part has some random pixels since PAL systems display more lines than NTSC systems. So there is a good chance the trak-ball modified version behaves the same on PAL.
Most CX-80 behave the same as CX-22. Some were factory modded to be compatible with Atari ST. CX-80 are nicer build quality than CX-22.
A long time ago I modded my CX-80 that had CX-20 mode with a rotary switch so it could be switched between CX-20, Atari ST mouse and Amiga mouse modes (Amiga mouse mode has two wires swapped compared to ST mouse mode). I've no idea were I got the modification instructions (I can't find it on my disk) but I found one CX-80 to mouse conversion on the web.