When we got the car back from dipping, there was lots of evidence that there was advanced corrosion on the inside of the panel working its way from the inside out. To do the job right, all of this needed to be cut off…
A shot of the inside of the rocker panel– you can see how thin things were:

The green is converted rust, there was no way that I could get to the inside of the rocker to get all of that out:

The top of the sill plate also was rusting from the inside out — see the extra holes:

And the rear of the rocker where the quarter panel overlaps the rocker panel was also very thin (with rust holes):

So, out came the plasma cutter and a few minutes later, the rocker panel was off the car so I could figure out what I have to deal with (you can see the dirt level on the rocker panel backing plate):

Looking back at the rear of the rocker, you can see how packed with dirt/rust this area was as well:

The wire wheel made short work of the crusty remains (though the shop is a terrible mess!)
Here is where we are as of tonight. The rocker panel is off the car. I still need to get the remains on the inside of the quarter panel, but that should not be too big of a deal. I have a rebuilt rocker panel to put back on the car and I will get that process documented when it occurs:

RX-7 GSL-SE Rear End
Motor Mount Jig Rental
My Classic Car