I can only go by my personal experiences. I fluctuate between 2X and 3X and have for the last 15 years. At WDW, I have found nothing that I couldn't "fit". Yes, 7dmt was tight, but not all that bad. Besides it's a very short ride so it is quite tolerable. I think that it depends more on where one is carrying the weight. Mine is mostly up front (belly), however I would think that if the weight is more across the hips it might be really tight. Space mtn. is out for me, but that is because of the effort it takes to get out of it, I still fit in. Sadly, I have been excluded from the Harry Potter stuff at Universal by perhaps an inch. If I could hold my breath for about 10 minutes I probably could have faked it.