As a previous poster said, for males its not a big issue, as new swimmers are made regularly. Just leave a gap ( a week?) between flying and doing the business. For females its another story sadly.
The simulation with 61uSv seems about right, and its not nothing. I work with radioactive sources and my planned yearly dose is 50uSv. Although health problems should not occur until much higher doses. Its not so much a problem of how high you fly, but how many hours per year.