Question about primal rings sizing

I am using a 45 fusion but dont know if this is my right size.. I am not hung but just average size but my balls tend to be high up.. I did their string measurements and was getting between 6 and 7 inches around.. with the 45 it doesnt sit right at base of cock near punic area unless I keep adjusting it and sliding it back. I ordered their spark 50 .. Which seems big to me because I am not packing a big package lol