Heres a view of the hole going down inside the rocker. I've cut away a flap that was about 1.5" by 3". I will not be replacing it, as now I have a nice relief hole for the junk that would otherwise collect down there. I do have to make sure that the structure of the car remains intact, but I don't see a huge problem there.
You can see the roundish hole at the end of that cut, which is in a problem area that will have to be repaired . I'll also have to get all those dead leaves and junk out of the rocker.
On this photo, I've circled that little problem area. I'll probably have to cut another small section out here, and weld in a little "L" shaped patch. I've actually cut just a hair more floor out than strictly necessary, but that was to make the patch more even, and to make the repair simpler and stronger. We'll see how that works.
Here's the same hole from the bottom of the car. The rotisserie Is making this job about 1000X easier. I can't imagine how much of a bitch this would be with the car on jack stands. Well, that's not true. I know full well it would be a super-bitch.
Tomorrow I'll get that small section cut out, and get working on the patch. I have a great little piece of steel for patching, and the .023 wire is in the welder. If all goes well, I may have this floor patched in a day or two (knock on wood).
I also tried a trick from the interwebs on removing heavy spots of undercoating. It's revolutionary: You heat up a putty knife with a propane torch, and scrape the crap off. Works better than anything I've tried so far--although I have yet to give good old fashioned oven cleaner a try. . .