Dura Ace 9-speed 7700 brifter welding fix?

[donat]

Hi,
I hope this is the right place for this type of question, I couldn't spot a specific mechanical forum to post in....

I've broken down a right hand dura ace 7700 brifter that shifts up, but requires fiddling to shift down. having cleaned it, and reassembled 3 times, I now realise the problem is exactly the one described here (bottom of the page): https://www.norvil.net/pedal/service/shimanosti/duraace9sti/detail.php
there's a throw away line at the end...

Some folks have asked 'can't I just file the burrs off the cage?'.
Sadly not. The profile is very important to syncronise the motion of
the inner and outer levers, as described above. You have to add metal
first. A TIG with a stainless steel filler rod would be ideal because
stainless work hardens.

Has anyone tried this? the TIG welding bit? I might be able to ask a friend, just seeing if anyone has tried before?