999 front clutch clearance with 6 frictions

In Tom Hands book on the Torqueflight
There are several performance suggestions
Even from other professional rebuilders,
Which I think is Cool In his own book!
Anyway for the front drum, most recommend .012 to .015 per disc.
I was surprised that Tom recommends .020 to .022 per disc with a tf-2 kit?
I never go less than .015 per clutch on a 727. when using the tf-2 kit Having .020 per clutch has nothing to do with the clutches burning out. I have taken factory trannys apart where there was .250 total clearance in the front drum and the clutches were mint. I would rather have a little too much clearance than not enough. I have built more than a hundred 727s with the -2 and -3 kits. Only a few 904-998/999 trannys. Kim