At 2 inches taller, but your weight, I carry it mostly in my thighs and rear end, I had trouble on Gringotts. Because they lock my legs in so I couldn't wiggle around and make it work. I was fine on Hogwarts. I haven't been since Hagrid's opened. Like Haystack said, tester seats. I was told at the Hogwarts ride by the staff outside that the tester outside wasn't calibrated correctly but the one halfway through the line was. That would have been awful to wait in that line and find out halfway through that there was a problem. Lucky for me I was a single rider so I just walked right to it. (Also lucky for me I didn't have trouble with that one.)
I didn't ride any other rides at Universal because for me, Universal is just what I walk through to get to HP.
There is an"Everything Pooh Sized" thread for WDW, but it doesn't cover Universal so much.