re: Which is the correct resin to use?

That's kind of what I am saying Dave. I looked at their FAQs, and maybe it's just the words used, but the many different links they provide for doing this and that, there is never one that says route out a pattern into wood, and then fill that. So I am mostly seeing links like for their Mirrorcast where they are filling natural faults in wood. Knots, cracks and stuff like that. All of which have irregular shaped holes, and surfaces compared to the flat bottom, and smooth sides of a routed hole. 

I guess what I am really looking for, should you just treat them the exact same way? There are all kinds of templates out there to route out openings, and the videos show them just pouring in some "goop", and later sanding it flush, but I've never seen where they name the "goop" used. I'm probably over thinking it, and any of it would/could work, it's just so expensive that if it does matter which you use it could be a costly endeavor, not to mention barfing up the wood, and work you did.

I hadn't seen as much about System 3 stuff. Seems every U tube person is using Total Boat, or maybe I'm watching the wrong You Tubers? :-)) 

I did fill out a customer question request, and sent it off. I'll see what they say.

Thanks Dave.