I just received a happs normal TB case top and a happs highball case top. I already own a highlip (green opti board). This is a just a quick review of them on the first night, not much playing yet.
Right off the bat, these tops are inter-changable. Remove the 6 screws, pop of the current top, put on another (line up the optiboard to slot!), replace the screws. Opti boards, ball, rollers, everything fits. Great if you want to upgrade/change your trackball.
Mounted on the happs normal TB mounting plate, I can't tell the difference between the highlip and the normal top. The highball needs a different mounting plate that I forget to buy. (D'oh!

) So I haven't seen the highball mounted.
One thing I noticed, the normal and highlip tops were cleaned up much better than the highball top. I had to sand down some ridges, wings, and bumps left over from the casting of the highball to get a good fit to the bottom half of the case, but not the other two. Not much a hassle, but I wonder if they're made at different places, or at least by different casting methods.
Lets see, what else, the normal top has a 1/16" inch high lip, the highlip has a 3/16" lip, the highball has a 1/8" lip. (The normal lip is drawn as having ~1/8" lip on the happs exploded view.)
I also bought the new red opti boards, but haven't tested them yet. 3x the number of resistors and capacitors of the old green boards, different chip. Might be a newer model opti sensor, but same shape and "make". I never had problems with the old green boards, but wanted to see if there was a difference.
I'll see if I can review all this stuff over the next couple weeks, and post the results.