On the plus side, you didn't pick the worst extractor to have hand made. You're probably in the right zone if you're factoring start to finish and maybe some live fire testing. Can't remember if you had contacted a gunsmith, but worth calling and explaining your problem - one might be interested or have a simple solution for you.
I might stop in to CSC to chat with the fellow there on my road trip this week.
Buy a spare extractor, put feeler gauges to the thickness you need behind the claw and and peen it down?
May be a cheap fix vs a day of labour.
You may really be onto something here pauls... I may just try that. I wonder if the fine edge of the extractor claw would break off? Probably not an expensive experiment anyway.