Great photo/diagram Leakey.
Every hatchback had to endure this built in problem which trapped moisture in the C pillar. My hatchback had the same problem that I had to deal with. I removed the outer skin (which you show in blue)

Then I removed the small inner skin section which is directly under the outer skin, as this traps in the moisture. I then made a new section in 0.9 mm mild steel and welded it back into position, follow by a light grind.

I also added a drain hole in the bottom of the rear quarter panel to release any moisture and rust proofed the inside of the C pillar. Hopefully this problem will never return. It's been 5 years since I repaired my hatch and no rust yet.
Regards Mick.
Edited by lxsstorana, 25 March 2007 - 06:02 PM.