It goes past 4.5 Gs all the time. Personally, I've never done it to myself, but it happens. I do remember getting a little over-zealous w/ a Mid in the back and pegging 4.500000000000000 Gs. I was worried about what the rear meter said, but fortunately, I guess I caught it in time.
I have had a few over Gs, a couple due to me not blocking over zealous students and one due to me avoiding going into a cloud during a cruise form wingover.
In CORTRAMID, I had a plane whose rear cockpit G meter would not go past 4.0, so once I was good and tolerant to G's, I regularly over G'd the rear meter.
Trust me, it goes past 4.5 no problems. That being said, with the exception of the CORTRAMID plane, I have never exceeded 5G's and never clicked the airframe accelerometers (in CORTRAMID, I put 9 clicks on, but the maintainers refused to replace the G meter in the front).