The change, apparently made just before this weekend, means that the scores of people who had previously been turned away from the ride because they were too large for safety devices can now enjoy it.
"Ever since it opened, there has been some discussion about how people couldn't ride," said Matt Roseboom, editor-in-chief of Orlando Attractions Magazine, which published a first-hand account of the change Saturday.
Roseboom said that since the ride opened in May, many guests complained they couldn't ride because their safety restraints wouldn't fully close. It was the only ride at Universal they apparently couldn't fit.
(The Harry Potter ride technically isn't a roller coaster but a simulator that travels on a track.)
Universal had installed special test seats at the entrance to the ride so larger patrons didn't need to wait on an hours-long line only to discover that they didn't fit. A green light and you were good to go. A red one meant no luck until you shed a few pounds. Roseboom said those test seats now also have a yellow light directing passengers to a special few seats with modified restraining devices.
Instead of hundreds of guests being turned away each day, Roseboom said, attendants told him only one was rejected in two days.
Universal acknowledges the change but isn't saying much.
"We routinely make minor adjustments to new attractions after having the opportunity to watch them operate, but we don't generally discuss the details of those adjustments," Tom Schroder, a spokesman for Universal Orlando said in an e-mail to ABC News.
The park tries to accommodate as many guests as possible on its rides, and after watching "Harry Potter" operate for several months, Schroder said, "we made some adjustments to the ride's overhead restraint system that would allow more people to ride."
"We're thrilled to be able to give more people the opportunity to experience this attraction," he said.
Amusement Parks and Obesity
Universal isn't alone in facing a -- literally -- growing problem. As America's waistline expands, amusement parks and their customers are looking for ways to adapt. Parks have to balance safety against the risk of alienating paying guests. Larger guests simply want to take the same rides as their skinner friends.
Adult men and women are about 25 pounds heavier than they were in 1960, and 65 percent are considered overweight, according to the National Center for Health Statistics. The average weight for men jumped from 166 pounds in 1960 to 191 pounds in 2002; women average 164 pounds instead of 140.
When Angel Pillow went on a family vacation to Cedar Point amusement park in Sandusky, Ohio a few summers ago, riding the roller coasters was one of the highlights for her husband and children.
But for Pillow, who weighed 240 pounds at the time, there was no joy, just humiliation. She waited more than an hour in line to ride Millennium Force, but when she tried to squeeze into a seat, her weight got in the way.
"It's just utter embarrassment. You get on there and are like, 'Oh my God, look at me. I'm too big to for to sit on this ride,'" Pillow said. "But it's not just that. My children were with me. I'm sure it was a pretty mortifying experience for them to see their mom have to get off the ride."
Then last year at Bush Gardens in Williamsburg, Va. she had the same problem trying to ride Alpengeist.
"That was, as far as I was concerned, the final straw," Pillow, now 40, told ABC News. "I just stood there crying. This is not good. I can't enjoy a family vacation because I can't participate in everything else that people are doing."
Pillow has since lost 25 pounds and plans to undergo gastric-bypass surgery to lose another 80 pounds.
"One of my goals with my nutritionist is to get the weight off so I can ride on that stupid ride at Cedar Point," she said.
Roller Coasters and Size Limits
Cedar Point is one of the few parks that specifies how big is too big to ride its attractions. It has a special section for "Guests of Exceptional Size" in its 2010 Rider Safety Guide. Its limits: "guests who exceed 6-foot-2 or those who exceed 225 pounds, have a 40-inch waistline or 52-inch chest or females who exceed 200 pounds or wear a size 18 or larger."
Ken Martin, an amusement ride safety consultant with KRM Consulting in Richmond, Va., said parks want to keep seats "as generic as possible because it's simpler and cheaper."
But a changing population has made the ride operators take notice and make adjustments. Today, Martin said, more and more parks are making accommodations.
"Skinny people, fat people, we all have money to spend," he said.
While extremely rare, there have been occasions where obese riders have fallen out of coasters because their restraint devices did not close properly or adequately protect them.
For instance, in the fall of 2001 a 292-pound woman came out of the restraints and fell to her death on Perilous Plunge, a water chute ride at Knott's Berry Farm in Buena Park, Calif. Changes were made to the restraint system and the ride reopened the next season.
In July of 2004, a 5-foot-3 man weighing 225 pounds died while on a ride then called Superman Ride of Steel at Six Flags New England in Agawam, Mass.
Too Fat for the Roller Coaster?
Chad Miller is one of those people working to revolutionize the roller coaster seat. He is a partner and engineer with the Gravity Group, a roller coaster design and engineering firm that is making its first wooden coaster cars.
"There's always been people who are too large for cars. That's always been a problem. The question is: where is the cutoff and how many people that is affecting," he said.
His firm is now designing lap bar restraints that are curved and can lock in at an infinite number of positions. So most small kids or large adults can safely be locked into the ride.
"We've seen the people riding the coasters and the huge variety of shapes and sizes," Miller said. Speaking with a lot of coaster enthusiasts, "A lot of them aren't shy about complaining that the cars are too tight or small for them."