My husband was heavier but taller (so the proportions might be around the same?) and he has had trouble. The "it'll be fine" answer might be true, but it also might NOT. DH was never able to ride the Maliboomer, much to his chagrin, and he wasn't able to ride what is now Goofy's Sky School. His legs are too tree trunkish to get them *between* the sides of the lap bar. If he could, then he could get the lap bar under his belly, but that would require skinny chicken legs, which he does not have.
Matterhorn nearly killed him on this last trip, he was squeezed into the seat and felt awful, and he's now under your weight. Space is still hard, but the lap bar there is different than on Sky School, so it works for him and he loves the ride.
Screamin' has always worked for him, but it's tricky, and he has had to have the attendant release the harness because he ended up with one arm stuck in a funky position.
Universal is NOT friendly to those who are Pooh (or Shrek, as Universal fans say) sized. I haen't been to the one in CA, but in FL DH hasn't been able to ride any big rides at all. He still loves it, but again, that's the FL version. CA's Universal is much much smaller with far fewer rides, and I highly doubt DH would find it to be worth going until he's closer to weightwatchers goal. Can you ask the question on the Universal forum here, making it clear you're talking CA, and see if people have experience there? I would hate for you to waste your money going there.
And yes, pull the seatbelt out all the way before sitting. For some reason it really makes a difference, even though no one can define why.
Best of luck to you!