I'm 6'8" and weigh 240 lbs. 7DMT is a tough fit, but not because of legroom. It's actually the width that I find problematic, and I'm not a wide person. I fit, though.
A few comments:
I can ride Space Mountain in seats 2, 3, 5, and 6. It's a tough fit, though, but if I weighed more, it would be a problem.
I find Haunted Mansion to be terribly uncomfortable. I have to slouch to fit inside the doom buggy.
I can barely hear the voice over in Spaceship Earth because my head is too far above the speakers. Again, I slouch.
I haven't ridden RnR in a long time, but I seem to remember that the shoulder harnesses are too low.
The front row of any boat ride is usually best for legroom (Pirates, Frozen, LwtL...).
All in all, I don't avoid any ride at WDW except for RnR.