brake ?

Need some help. When mounting master cylinder to the firewall, how far should the push rod go inside the master cylinder?

I would guess it doesn't really matter as long as you don't bottom out the cylinder and damage the unit.

The piston has to come all the way back when the pedal is released, there should be a little bit of slack at rest. Otherwise the fill port won't be open, and the cylinder won't fill itself.

My understanding is that the piston should not be depress unless the brakes are being applied?
A little more information is that they are manual brakes, disk brakes all around.