I think for a race car folks keep it simple. These discussions on other sites go on for 10s of pages. While folks understand all the individual piece, not sure folks have thought through all the integrated elements. Some times vacuum adv advances for motor needs, other times it retards timing.

Most know generically what vacuum does, but I doubt many have mapped vacuum under driving conditions.

For HP motors with dual points in the day, before emissions you would have around 8 to 12 degrees initial, and get another 16-22 out of the mechanical, with a light and heavy (gapped) spring. Vacuum added or takes away another 18-24 degrees. Stock motor, stock calibrated carb designed for the motor and the distributor. Once CAP hit in 66-67 initial was between -2 to +2 usually around 0 for BB certainly hemi. Mechanical gave 30 degrees, some unit 34. Vacuum still around 22.

So as you go down this path, what changes have you made. What is engine vacuum look like intake/ported. When does ported come in, or is it already on at idle because of cam, carb change and other things tuning changes you made for idle.

Seems a little dangerous to have a high initial, and vacuum on intake, especially if you made changes to mechanical adv springs to get all in earlier. As stated earlier, even when vacuum goes toward 0, the vacuum timing retards slower, and with mechanical advancing faster, your probably pretty close to detonation.
If your doing this in your drive way in neutral your really not testing a loaded motor.