Two comments
first the ATD was built to react when 38 BTDC fully advanced was a suitable setting because we still had decent petrol
The slop we have nowadays has necesitated moving the timing towards 35-34 BTDC and speaking to Roy Price shortly before he died he was thinking (or actually was reducing?) the throw of his mecanism to allow for this.
personally I think measuring the throw of the ATD is the first step. if we think 4*deg BTD is a kick start figure then a throw of 15 degrees should be in the ball park
* alter to taste