At 135 ground school the instructor said the logic behind the difference in O2 requirements for 121 and 135 was due to the difference in the size of the equipment. An airliner being larger, a pressurization leak would not be as bad as a leak on a the normal 135 airplane. I realize the legacy is mostly a 121 airplane that flops just uses as a 135 airplane, but the regs clearly state over FL350 in 135 service one crewmember must be wearing the mask. If the feds change the rules then no problem. Until then you do what a professional pilot does, fly by the rules. Do you think options will take any of the heat or help you in any way in case of a violation? HA! Again do nothing illegal for or against the company.