How did this guy get this job? What are the qualifications? Hand size? A gentle touch? Both?
If placing your hand too high means you want to be friends, the middle of is the safe zone, and and too low on her back means you’re probably getting slapped, what does “hand placed firmly on butt” mean? Death? I seriously advise you not to try and experiment with that—even if it is for scientific purposes.
Getting sent up river simply isn’t worth it, no matter how big the booty.