Another main problem may come from the necessity to open the Cartridge without breaking 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 in these pictures).
The Multi EPROM cartridge shown here seems to be of a proffessionnal professionnal quality. The Chip socket (ZIF Type) is epicly good as it allows the removal of the EPROM/ROM without harming it.