Quoted from Klemp:
Let me clarify: The arcade had my 10 letter name showing on play screen. I can’t replicate it at home while playing. The arcade also allowed for Highscores with 10 letter name.
On my machine, the Highscores allow for 10 letter name rather than 3 letter initials — but my play screen (pictured in first post) does not.
To further complicate the question:
(This is on a Rush machine, so it's not exactly the same, but I would've thought the IC stuff would be pretty much the same across any Stern machine that supports it, so...)
I have my machine configured for 3-letter initials for high score display. And yet, the player name on the play screen comes up as my username, which is more than three letters.
In other words, I'm pretty sure that the setting you found, "HSTD Initials" does not actually have anything to do with how the player's name is displayed while actually playing a game. Now, what does control that, I don't know. But at least you can be reassured about the seeming disconnect between the setting you're looking at, and the way your name is being displayed when you play. That seems "by design" as far as I can tell.