They measure you with shoes on and we found them to be very strict (which I think is a good thing). On the board at the front of the park, it looked like DS was ok to ride, just making it. When he got in line for DD he was about a hair below the line, it was so close it was hard to tell. After much discussion the ride attendant said he couldn't let him but because he wasn't completely sure he would call the manager and have him measure my DS. We said no thanks, knowing that it's a safety thing, wasn't worth it. Let's just say DS was more than a little disappointed, gives us an excuse to go back though. Funny though, just 2 days before he rode Krakken at SW which I think is also 54". No question at all there.
In Feb. DS7/1st grade (in Jan. '06) went to the dr. for his check-up. Having bought new sneakers the week before, I asked the nurse to measure him in his sneakers. After a strange look, and a "I don't get THAT request too often", I explained we are gearing for 54" for vacation. She obliged, and he was.......53.75"!!! 
So, I'm not sure of his height now, but I think he'll grow that extra 1/4" by the end of June. A few weeks after his check-up, he ended up with croup-cough and was on steroids too! I'm sure that helped a bit. And, I was even thinking ahead, and when I bought those new sneakers in Feb/end of Jan., I bought two of the same shoe because I knew he'd wear down the soles on the first pair he's wearing. I'll just have him wear the new sneakers for a couple of weeks before we go to break them in! We'll be going to Dorney Park (DH company picnic) on June 3rd, and they have 2 coasters DS is absolutely DYING to ride...height requirement for those=54". So, it'll be a good test to see how tall he is!!
