Typically a restrictor in the front clutch apply passage
is used with a stock pressure valve body like the Trans
Go kits. They use around 9 springs in the front clutch
The restrictor along with nine springs helps eliminate
the overlap. A purpose built RMVB with higher pressure
does not call out a restrictor but uses 12-15 springs
Also two springs in the front servo to help unload the
kick down band faster. Along with a 3.8 or 4.2 band lever
to allow a clean 2-3 shift. This would be for a VB with
no low band apply in 1st. If you have band apply in 1st
you might need a higher rate spring in the low/rev servo
to allow a clean 1-2 shift. Griner VB uses enlarged
low/rev servo passage to help unload servo upon
release. In a Transbrake application, the 15 springs
help release the direct clutch faster when you release
the button to prevent the direct clutches from dragging
during launch. When the line pressure is 180-200,
typically have to reduce the band lever ratio to 3.2 or
2.9 so the kick down band strut will not deform. A lot
of testing is needed to fine tune combination. I know
Randy who sells many parts on the board has done
a lot of testing.