I'm at the stage of my 727 rebuild, with transgo TF-2 street kit, 4 pinion planetaries, 3.8 lever - making decisions on front clutch clearance, # springs, whether to use transgo clutch flow restrictor, etc. From what I read, these decisions can all influence 2-3 shift overlap.

Assuming there is no magic formula, is there a set of guidelines which address these (and other?) variables in terms of optimizing the 2-3 shift?

The trans is going behind a mostly stock, street 440-6, 3.23 gears, 70RR.

to add ... what type clutches, line-pressure, KD band ?

Here is what I did when I just put mine together. I talked to the maker of the valve body and they told me to run 12 springs in front drum and set clutch clearance at .100 with flat snap ring. Was also told to run billet front servo or old style or plug port in servo and stack full of washers to make it solid if it is a later cushioning servo. I have only drove it a little but it shifts great.

If you decide to use a large number of springs in the front clutch, you're stuck with that decision if you don't like the shift. Using fewer springs and relying on the flow restrictor allows you to tune the shift without having to remove/disassemble the trans.

i used 10 springs in mine stock was 8 so i thought ten was a good compromise , i went with billet servos and tf-2 kit car shifted nice and clean 2-3 .