It went right in to the old shore power connector's mounting holes. No filling or drilling required. The plug has a nice firm feel to it with no tendency to get accidently knocked loose like the old Hubble one did (my shore power connector is located in a position such that it's easy to accidentally bump it as you come aboard or leave the boat).

I also replaced the OEM AC Selector switch and the wiring between the connector and and the selector switch. The connection to the battery charger was also moved to the shore power side of the selector switch so that it is no longer possible to try to charge the batteries by running the charger off the inverter. A couple of years ago, we were cruising down the California coast and pulled into a marina in San Diego for a couple of nights. We plugged into shore power without changing the selector switch. This would have been fine, but my son had been using the inverter earlier and had forgotten to turn it off. As a result, after plugging the boat in, when I glanced at the panel, the meter showed that we had good AC power (probably why I didn't check the selector switch) and turned the charger on. It wasn't detected until the following morning when I saw that the batteries were way down instead of being full as I had expected to see.