I'm 6'0 and 290 lbs and I have only been denied 3 coasters so far.
1. Abismo in Madrid - clamshell Maurer X-Car restraint. This one was weird as I have always ridden Hollywood RRR and ridden all of the Skyloop's without issue. Perhaps this was an original and a bit tighter.
2. The Mine Train at Ocean Park - ops didn't help on this one, and the lapbar was kind of bulky and hard for me to get one more click. I was solo, and if someone was with me I think it would have been fine.
3. Shambhala at Port Aventura - Yes, this B&M requires more clicks than the others. I've heard this is the same for the Japanese ones. I think it's 3 instead of the standard 2. I was able to ride Fury and Mako the last 2 years but not Shambhala. I just need to get back to my college weight of 265 and this should be a non issue.
RMC restraints are tight but I can get those myself by crossing my legs, pushing down myself, and then even uncrossing if I want. But no park has had an issue yet. I feel like SFM set their tolerances tighter on Medusa as that one was harder. Kentucky Kingdom's seemed to be the easiest, the ops didn't even have to push and of course Dollywood won't even try to push and I rode Lightning Rod at this weight.
Intamins lap bars and OTSRs are tight but never been a problem so far. Actually the NEW restraints they are using on Red Force, Taron, new hyper coming to Poland, etc are extremely comfortable and no issue at all.
Also have no problem getting the modern Mack trains closed. And they have more room in the back row I think.
B&M OTSR's require me to use the big boy seat on most coasters. I was able to get in a regular seat on some of the Batmans. Just need to get back to that college weight for any seat to be fine again...but I am glad to see more parks putting the bigger seats in other rows including front and back. The vests just barely work for any seat so I like those