I'm dealing with the same issue. I usually use Furrion connectors and their square connector is pretty much the same size of the Park Power plug. The square plugs don't quite cover the big hole. You also have to deal with the three rivet holes.
I usually install an access panel to get to under the dinette bench and move and drill a proper mounting hole for the square plug. In my S-16 DX the power plug was located over the side running light
so I now also have to deal with the large Scamp
power plug hole.
This is my plan. The rivet holes are about 4.5" in dia. I plan to fill them with white Marine-Tex, a real close match to the gelcoat. The round plug I selected outside dia. is 4.5" so it just barely covers the rivet holes. The mounting screw holes on the connector are 3.5" and it looks like the scamp
big hole is 3.25". I plan to install a backer plate inside the trailer first and drill new mounting holes.
This is the connector I plan to use. http://www.amazon.com/Furrion-Ltd-Ro...n+30+amp+inlet