Thank you!
If you look at your upper triple, is one side higher than the other? If not, I imagine that rather than latheing he was able to use "two spring clamps on each side" as you mention, in order to force the cartridge base to seat all the way into the oil lock piece. However that seems hard to believe (by me) that the aluminum oil lock piece would be able to be widened without really being warped and unable to fit into the fork tube....
Here's the issue with the oil lock piece width. The bottom of the OEM compression side oil lock pice has a small inside lip that my professional mechanic over at Superplush said we had to lathe in order for the Matris "bottom support" piece (that's how they refer to it in their instructions) to fit.
The "bottom support pieces" are actually the same size in the Matris Kit:
And are different sizes in the OEM (in this photo compression side is on the right, showing it is narrower in OEM):
