What kind of filter basket are you using in your portafilter?
If you are using a VST or a Strada...take a look at the Cafelat Royal tamper. It is 58.35MM with a 0.05MM variance. Fits those baskets perfectly...and would probably fit any good 58MM basket.
I have both the Cafelat and the Rocket tamping stations. I like the Rocket a lot, and don't use the Cafelat any more.
Um, what?! Will have to look up half of what you wrote tomorrow but I'm still using that little Bialetti machine which is 55mm in diameter...if that is what you've asked..