I'm not sure what you mean by an Edison Platform. Is it the Clamp-on Platform - Center Mount
or something like that? As I see it, the deal with installing accessories on boats is there is not a huge market and there is a lot of variation it what combination of products people use, and I always expect a little field modification is going to be required for a good custom installation.
If I were buying that product, I'd rather drill the holes I need than have a lot of extra wholes I don't need.
One thing to consider is that once you drill oversize holes large enough for the connectors, you might want to put some rubber grommets like these
in to protect the cables, and that will give you a more finished look, hide the fact that the hole is larger than the cable, and protect the cables from chafe.
I agree with Garmin - don't cut and splice, that's asking for trouble down the road.