123 Distributor vacuum advance set up and curve, Advise on seting up the vacuum advance curve on 123 distributor Options

[Clydeskeeper]

I have searched the forum and watched too many YouTube videos. I am either missing the answer or just don't quite understand.
I am replacing my distributor with a Bluetooth 123. I am a little confused on setting up the vacuum advance curve and maybe even the mechanical curve. On a basic level, I understand that it needs to go from a static of 10 degree at idle up to 27 or even a little more at 3,500 rpm's. Of the videos I have watched, seems like most are not even using the vacuum advance part and just using the mechanical to achieve the above curve. Others go into details I just don't understand including using the vacuum to retard the timing at certain rpm's.
Is there a simple answer and old guy like me can understand? I grew up with cars that actually had mechanical distributors with points and carburetors for fuel delivery. So these concepts are not completely foreign to me.

Just for reference, the engine in question is a modified 2 liter that is now 2549cc with dual 48 Webers.

I await your thoughts, should be interesting at always.

Robert!

[rjames]

Retard was an old thing to reduce emissions at idle. Don't mess with that, it's a mistake in the 123. The original design had an analog response to vacuum but the digital does not and it can end up retarding your timing at cruise. A bad idea

Tell me more about this. I've got a non-bluetooth 123 distributor in my '75. It's been a while since I installed it, but I'm pretty sure I've got it set to a setting that was supposed to mimic the stock dizzy's retard function I think.

The two options as a replacement for my stock dizzy according to the 123's documentation was setting 2 or setting B.
I assumed using setting #2 would result in a high idle, but maybe not? Am I leaving performance on the table by using setting B? Both have a max advance at 2700rpm but it shows differences as to when advance starts and ends. (IMG:style_emoticons/default/confused24.gif)