I would error on the side of being careful, and I'm usually not that mom. My kids are very tall for their ages. We had a trip about 2 months after Slinky opened (38" requirement) and our 2 year 6 month old was tall enough (by a few inches). It was WAY too much jerking, etc. for her. I had to use my entire arm to hold around the top of her head to her far shoulder to keep her head up.. and use my other hand to help her keep leaned back. We rope dropped and ran, so our wait was only about 20 minutes, but it was a waste of my ride, and she cried (she's not a kid that gets scared on stuff like this normally). I think the average kid should be 4+ to ride slinky - it's not just height. Since you can see the track, I should have just look up and made my own conclusion, not just the posted height requirement, but when in a rush, so excited, etc. - I don't have a good excuse I just didn't. Now that I'm looking around barnstormer is only 35".. and it's jerky too IMO. I would read what others say, not just follow the height limitations.