I was influenced initially by the work of a Texan who published his methods and materials on a different forum a few years ago. He got me thinking about particle sizes and ultrasonic frequencies.
I began with a 60 kHz Vibrato machine, which worked very well. A number of factors led me to believe that longer, gentler cleaning was a more effective and safer approach. So, I bought the 80 kHz machine. While the cavitation bubbles of the 80 kHz machine are most effective at removing smaller particles, I found that if I ran the record for a longer time those smaller bubbles did remove larger particles as well as the 60 kHz system did. Also, I experimented with timing motor speeds and the cleaning solution mix.
My testing has been by ear. I listen to a record and clean it until I am satisfied that it has stopped improving. This listening test led me to conclude that the 80kHz machine would clean more effectively than the 60 kHz machine.
One downside of my approach is that record cleaning takes more time. Since I enjoy the process that is not a burden for me.
I use cork stoppers large enough to cover the record label between the records as I mount them on the spindle. These cork rings are 1.25 inches thick. I mount three LPs at a time, which leaves them approximately uniformly distributed between the tank walls in the bath. I did not perceive improved listening results when I have increased the distance between LPs (2 LPs per cycle). When I tried more than 3 LPs per cycle I did begin to see some impairment of the water circulation movement. So, I've stayed with 3 LPs.