[horsa]

The metal in those areas was originally crimped down at 90 degree angles on each of the long edges. During production, they pressed the crimped panel in between the armor sections for welding. I used the thinner cut-off wheels/discs on my 4" angle grinder to remove the old sheet metal. Make the cuts near the welds but stay in the sheet metal to make smooth and fast progress. A cutting torch could be used as an option but you don't want to weaken the old welds or the armor so might be faster but leave more to grind later. After the sheet metal panels are gone, use grinding discs made for stainless steel welds to grind back the remains towards the armor walls. It's a lot of heavy work to be sure. I had used cheaper grinding discs at first and went through them pretty fast. The more expensive discs for stainless will go ten times further. Cost might work out close to the same but you won't be changing discs out every few minutes and won't have as much dust from disintegrating discs.

When replacing the metal, we used flat pieces without the crimps. Figured it wouldn't be in combat anymore and the new metal and welds would be supported by the long welds and old crimped remaining edge that is on the track side. Saves overall grinding and welding that way. And there is no risk of cutting into the armor from working at awkward angles down there.