[Roadsters] How do you tighten that nut? You don't with big hand I guess!

[Graeme]

  The space under the compressor was so small I could barely get one finger
tip on the nut of the valve. Can you say "time to modify the drain valve"?

I've got the same problem although my hands are not huge.
Try sitting the compressor on a couple of house bricks to get more space
around the drain valve.
I've got one under each wheel and a slightly narrower one under the foot so
the tank slopes towards the valve ; )