PSU and power connections

[Screaming_Rabbit]

Hey Folks

I have another PSU and power connections question for MIDIBox LC.  ::)

First what I wanna do:

I have 3 switching computer PSUs and one transistor regulated 5V PSU, which I wanna build into an external 19" / 2HE rack case. Having a 6 core cable going to the controller and inside the controller on 6 copper rails going from left to right for distribution. That's the way it's done inside the AMEK / Fairlight Fame (little bit of copying ;-)

First question:

Is there are problem, connecting all the grounds / 0V to one common line inside the rack case?

Second Question:

Since according the ALPS MF Datasheets one fader can draw up to 800mA, it's possible that I draw 24x800mA=19.2A plus 5V/2A from the Core, plus 5V/4A from the for backlight LEDs... does the common ground cable have to handle 25.2A or is this a wrong calculation?

Thanks and greets

Roger