So for a thumb rule you can say .015 per clutch.
4 clutches .060, 5 clutches .075 and so on.
The springs in the Front piston don´t have to be that much, but 7 is a littlebit weak.
go for 9 or 12.( KD Lever 3.2 or 3.8)
When you have a high ratio KD Lever,Like 4.2 or higher, add more springs...