Stripped screw hole on ultegra di2 front derailleur mounting

[wch]

The screw was over-tighten so the hole got damaged and stripped. Now the screw can't be screwed in the hole fully, so the FD can't be firmly mounted to the frame.

I've tried JB weld, but it isn't tight enough to hold the FD steady when it's shifting. Any idea other than buying a new dera? Also I'm looking at helicoil insert as a possible solution, anyone has experience?