If the bottom notch was beveled like all of the other notches, I would think the headrest would then be removable. A bench grinder should be able to take care of that.
Is the pin be too deep/long to allow reinserting the headrest?
Can the sping/pin be removed without removing the plastic sleeve? It looks accessible.
Here's what I'm thinking...
1) remove the seat back
2) pop off the spring/pin assy
3) remove the headrest
4) bevel the last notch
5) reinstall the headrest
6) reinstall the pin assy
7) reinstall the seat back
Gregg
2001 Proton Yellow #1379