I have not taken the entire mechanism apart past the weights and springs, but the spring posts on the plate end are round. Are they mounted eccentrically? I'd assumed they were permanently riveted or welded in place...
Now we're getting into SSSS.
The real funny part is that this is common knowledge in the slant six crowd. Go figure.
Taking the shaft out is a bit of a pain. It's easy to crack the nylon collar when driving the roll pin out or in.
You can turn a screw driver into a adjuster tool.
Of course its easier file the fit with the distributor disassembled.
Anyway that's an option.
There's no guarentee it isn't already maxed out in the direction want.