Here's a photo of the structure behind the outer cill (sill) of a BA 323f
This is the remains of my donor car, it's upside down, standing on the door pillars. (The outer cill has been cut off to patch another car)
It is reassuring to see how much stucture there is in those crash zones, and this pic might help anyone hoping to use e.g. Waxoyl in their cills.
For reference, the two small rusty holes are where the bottom of the front wing would bolt on.