Guess I'm not following your math; as plotting out a 30 degree stock rotation does not prove your calculation. Either by staying on the stock center line or the eccentrics tangent point, witch would be its center line.
So guess I need educated on your logic or I'm not following your descriptions.
I'm a big proponent of CAD drawings to visualize and verify.
For me I can see a Cool idea for a macro on my 6 axis lathe, but I will still need to calculate in tool nose radius for my use.
Thanks for the inspiration. I do some arcs, wedges and twists now but never looked at eccentrics.