I am not using an led just the standard 12v lamp form Happ.
From what I've seen here... It looks like using an LED will actually make the trackball brighter which is what I don't want. I think I will try underpowering via the 5v and see how I like that. Personally I like the way the ball looks not lit. I think with using the 5v it would look not lit in daylight, but when dark it would give a very mild glow.