Boardwalk in Santa Cruz, CA
One person was asked to get off a roller coaster in front of everybody because the bar would not go down. Another person (5′3, and around 300 lbs) tried to ride the Big Dipper rollercoaster, was asked to get off the ride, and was refused a refund.

Disneyland in CA
300+, 410lb, 310lb, and 3X people fit through all the turnstiles and fit on every single ride without problems. One woman complained that the rocket jets were uncomfortable and some of the gates were smallish, and recommended not sitting in the front car of Space Mountain. Disney did not complain that she needed to take a whole seat meant for two. Many of the rides are accessible for much larger folks as well (i.e., Pirates of the Caribbean, Splash Mount, Jungle Boat, and Matterhorn). Star Tours may not be entirely comfortable; it has theater-type seats. One person needed a seatbelt extender for Star Tours and they provided it without a fuss. And on Main St., the Clothier store, the Disney Emporium, and Tomorrowland all have large-size clothing (some up to 8X). The seats in MGM Studios were somewhat uncomfortable for one person. One person couldn’t fit through the turnstiles and ended up lifting himself over them.
Disneyland is very accommodating to people with physical limitations and will assist people in getting on and off the rides. They have wheelchairs available for a small deposit.

Knott’s Berry Farm in Orange County, CA
A super sized woman had no problem on any of the rides she went on.
Another person warns that many of the rides, with the exception of the log flume and the California River Country Raft Ride, are not size friendly, including the three major roller coasters. One of the roller coasters (Montezuma’s Revenge?) may be bad for people with back or neck problems. (”Starts on a short section of track, catapults you forward, through a loop to a near vertical incline at which you fall and reverse the process passing through the start station and going to another near vertical incline and you then fall back forward and stop in the station”) The fried chicken dinner at the restaurant is recommended.

Lagoon in Farmington, UT
One person had a bad experience with a roller coaster — the bar went down but the person was pinned very uncomfortably and had a hard time getting the bar to release.

Great America in Napa County, CA
One woman didn’t fit on one of the rides, and they gave her and her partner passes to go to the head of the line on any other ride (to make up for the fact that she waited all that time for the first ride). A 5′4″ 220-lb size 18-24 woman fit on all the rides, but just barely on the wooden rollercoaster. A 5′7″ 340 lb. person could not fit on anything, except one rollercoaster (not the wooden one, presumably).

Six Flags Magic Mountain
Two people reported bad experiences. One concerned the roller coaster. Nothing was posted about a size limit, but the safety bar would not lock and the person was asked to leave the ride. One person commented that the amusement park is very hilly. One 300 lb. person fit onto the Batman and Superman rides.

Wild Bills at Stateline, NV
Roller coaster is reported to be a very tight fit. Operators were snickering and giggling. Too young to be safe (the operators) and rude.

Cedar Point in OH
People over 6′5″ or having over a 50 inch waist or a very large bust or chest may have problems with the Raptor. People with over a 50 inch waist may have problems with the Mean Streak, the Corkscrew, and the Magnum 200XL. People with over a 60 inch waist may have problems with the Iron Dragon, the Blue Streak, and the Gemini. All the water rides and standard rides should accommodate folks with less than a 60″ waist.

Kennywood Park in Pittsburgh, PA
One reader was humiliated by ride staff.

King’s Island in Cincinatti, OH
A size 20W-22W woman visited here and found all of the coasters comfortable. The roomiest was Top Gun, and one coaster was a little snug. The Flight Commander ride had a sign saying that “especially large people” might not be able to ride, but our intrepid tester had no problems. On the other hand, another woman (size 18W or so) couldn’t fit on several of the rides. A 400+ pound man was comfortable in the Skylab and short log flume water rides.

Six Flags Over Texas
Two mid-sized people had trouble getting into the Texas Giant ride. However, one person who is approximately 280 lbs and 5’8″ girth did not have a problem here except for “occasionally a tight fit.”