I will repeat my dribble once again.
MSD like this will produce a hot spark for 20 degrees of rotation, give or take considering resistance, etc.
This means advance is out of the window for this period as spark will be present and not need to be advanced.
I would recommend disabling the vacuum advance as well. Checking total timing and desired will determine what advance could be tuned. FME it ain't gonna be ported/ manifold vacuum. Stiff springs on the weights wil get more advance as the mill is screaming.
Lock it all out and determine base timing (where it seems to run best).
Check total advance and see specs. (not that that matters!)
You might be surprised. Starts good. Rattles on accel, retard timing until rattle is gone. Binds on start? Too much advance. Heavier springs/lockout.
Hard to start? Retard timing til starts easily. No rattle up top? Window too narrow. Lighter springs.
You can change just 1 spring to get incremental.
Tuning.