Hi all! I thought I would reply to my own post with my LEGOLAND experience, in case it would help someone else. As stated, I'm around a size 22, with most of my weight carried in my stomach area. As a matter of comparision, I've never had trouble riding anything at Disney because of my size. I was able to ride Harry Potter and the Escape from Gringott's at Universal, but was not able to get the green light on Forbidden Journey.
Here's the low down on coasters at LEGOLAND:
I was able to ride Project X without any trouble. I was able to ride Flying School as well, though it did require a second employee to buckle the safety belt while the first kind of squished me into the harness. They were very nice about it, but it was definitely only something I would want to ride once. I let my son ride a few more times by himself--I didn't want to have to go through the experience of getting buckled in again.
Coastersaurus was a no go for me. I was too big for the bar to catch. Honestly, that was okay because the amount of leg room in the car is ridiculous--I'm 5'2 and felt like my knees were in my throat. Not sure how tall people do it. The bad thing about this was that after they told me I couldn't ride, I had to step over my son to get to the platform on the exiting side of the coaster. This was fairly awkward, just because it was hard to do. Also, I'm not easily embarrassed over my weight (I figure that it isn't exactly a secret that I'm overweight, so I try not to let me bother me), but I did hear someone on the ride make a comment that I had to get off because I didn't fit. I don't think they were trying to be mean, but that was a bit embarrassing.
Dragon was also a no go--there sign states that there is a 330lb weight limit per car. Between myself and my son, we were pretty much at that limit, so I didn't want to chance it. Looking back on it, I could have just ridden in my own car. They would have let me and it would not have been a big deal, but I was kind of roller coastered out by that point in the day, so I just let him ride by himself.
All in all, we had a great day at LEGOLAND. It isn't Disney, but it was a nice little park. While I had issues with fitting on some of the coasters, it really is the kind of place that is more for kids than adults. My son absolutely loved it, so I was glad we went.
Hope this helps!