Just installed my 3" RGB upgrade kit on a
Happs Trackball and I found that the included spacers aren't thick enough. The LED's actually hit the trackball, even when I only very loosely tightened the screws.
I went to Home Depot and picked up some #6-32 (35) Nylon Machine Screw Nuts and added them to the mix for more distance. Now the TB spins freely and everything it nice and snug. I even found that the Screw Nuts threaded onto the screws and kept them in place before the install. That really cut down on the fumbling and aligning when I mounted the lighting unit.
The light intensity on the trackball seems absolutely perfect. Not too bright, doesn't distract. Nice even lighting, very diffuse. On my ball, there seems to be a very tiny imperfection, a bubble near the surface on one area of the ball itself, but it's not really noticeable, even when lit. I only mention it so that Randy might be aware, from a production standpoint, that it could create issues down the line. The ball itself is perfectly round, and the weight doesn't seem like it'll be an issue, even though it is a little lighter than the stock Happs 3" ball.
All in all, I'm very happy with the purchase. Another fine product from RandyT.
Here's some reference pictures of the install:

The Nylon Screw Nuts holding the screws in.

The washers (included with the kit) are lined up; ready to drop in the board.

Installed.

Now the LED's are below the dangerzone.

Balls spins perfectly.