Have a look at some of the QSL cards received from stations who were permitted to transmit on 6 meters. I could only listen or talk back on 10 meters. At the time, most 6 meters stations listened around 28.885 MHz.
Conditions were so good, that I could hear European stations via backscatter on 10 meters.
My 10 meter transmitter was very poor. I converted a CB transceiver, it had about 5 Watts output. The antenna was a simple dipole, so some 6 meter stations had difficulties receiving me.