If that happens, you weren't riding right. If your center of gravity isn't in line with your legs, you'll use your legs to push yourself up against the seat and away from the floor. That's not good, because your legs are fighting what is effectively several times your normal weight.
I've said it many times: The best way to ride a B&M stand-up is with the harness just above your shoulders, leaning into the harness away from the seat, with your feet all the way to the back of the floor. This aligns your weight right over your leg so you are supported by your bones, not your muscles.
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Jeff
Webmaster/Admin - CoasterBuzz.com