I'm also trying to help him. First off How many slants have you built? I have been building and racing slant sixes since 1974. I also converse with many other slant six racers about what works and what does not. Chrysler does not recommend 30 degrees total advance, that is a number performance slanters have found to work best, MOST OF THE TIME. Usually when you start going more then thirty degrees total, the MPH in the traps drops off.
And if you will notice, I did not say this is all written in stone. I have stated "IN GENERAL". As you said all motors are not the same. One of the motors, I am running now, has 24 degrees advance from idle to 7,000 rpm. It has a locked distributor. It is a 170cid slant six, that has made 358 foot lbs of torque on a chassis dyno, and pushes a 3250 lb car 13.2's at 98 mph 1/4 mile.