I hit the rev limiter once, I was in 4th gear. Put the hammer down and didn't let up until the needle was right at 7K and that is when the engine hit the fuel cutoff limiter. I don't remember exactly what my speed was I think it was a bit north of 140MPH.
So I think my tach is actually fairly accurate still, being that the limiter is set at 7200, that would mean it was reading only 200 RPM low at that point.
Nearly every time I drive my Z, I do at least one short run through the gears to at least 6K to make sure the secondaries stays clean and working.

And every time it amazes me how it just keeps pulling and pulling! Not to mention the awesomeness of the scream of the LT5 at those higher rpms. Love it!!