In discussions with a local indy he says the way he has them fixed is to remove the inner plastic covering and cut a hole big enough to get back in there and weld a new one in. The part number for the new "mount" is 123 630 03 20. Your way of doing it sounds easier. Also, that is what is called "plug" welding. My 240D needs this done on the drivers door and I will probably take care of it when I get it painted.

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Jim