If you are being safe and paying attention is is not more dangerous than a small engine.

Buy the Way, Many full scale aircraft are started by hand with no restraints, and nobody in the pilots seat. I once tried to start a friends J3 Cub (full scale) but couldn't give that little extra to get threw the second compression , But ol Gene at around 70 years old can do it on the first try almost every time, I believe the plane has been in the family sense 1948.