Hmmm...have not seen anyone have problems on M:S due to size, however, I have to admit that I have not seen anyone of your height or chest size try to ride. I know that there is a maximum height for the capsule but I don't know what it is for sure. As far as the restraint - it comes down from overhead and locks into place, similar to how the RnRC restraints work.
I hope you are able to ride - it is great. Good luck!