Outer Limits 4x4 Board

I am going to be fitting an external air oil cooler to my automatic and bypassing the factory water cooled unit.
I have some questions i hope someone can answer.

1) If the height of the top of the cooler is higher than the full mark on the gearbox, does this mean when the engine is off that oil will drain down out of the cooler back into gearbox sump, leaving the cooler only, say, half full? Is this a problem?

2) The way i am installing the cooler it is sitting vertical, so basically it has one header tank at the top and one at the bottom (it is sandwich style cooler) does it matter which fitting i connect the feed and return lines? ie. should oil be fed into the bottom and work its way up and out of the top fitting, or top down?

More questions may follow!

Thanks

The height wont matter. Drain back is not an issue!

I would put the hot oil in the top and cool out the bottom! Remember heat rises Thats the way a radiator generally works

Thanks mate!

3) can the system be flushed through the oil cooler lines? Eg put pressure line into empty bucket and suction line into clean oil. Will it work?