Oh, DDog, this is a fun one.
I've found that when passenger pegs are mounted conveniently for the builder and rider, the passenger is uncomfortable.
When the pegs are mounted for passenger comfort, it's challenging for the builder, and cumbersome for the rider (ankle *klanks* during kickstart).
Now comes the demented part. What kind of relationship does the rider have (or want) with the passenger? Positioned correctly, passenger kneecaps make great armrests. Can get creative here.
FWIW, I never liked taking dudes on as passengers.