Of course the most important chip remains the [[Amstrad Cartridge Identification Device| ACID]] and should be treated with exceptional care.
Another main problem may come from the necessity to open the Cartridge without broking anything.
Instead of filing a big hole, you may use somle extra connections (wires), smaller holes and then the ROM socket is fixed on the cartridge (as seen on those pictures).
The Multi EPROM cartridge shown here seems of a proffessionnal quality. The Chip socket is epicly good as it allows to remove the EPROM/ROM without harming it.