I've never done this, but these discussions usually make me think.

If a person was trying to thread that needle, get the engine to spin and fire at one RPM and timing setting, then have the ignition go to near total or total when it starts so the dumb thing will idle and respond... why not use distributor advance flyweight weights to adjust it?

Springs only give you a few options. Weight changes can be infinite. They do it with clutches.

Add a dab of spot weld with a MIG out on the heavy end of the weight. Get too much you can grind it off. Or drill and tap some machine screw holes and add screws and washers. More weight should bring advance in quicker. Keep the flyweights equal.

I would want to do this on a distributor machine. Probably be a PIA trying to do it on an engine.