When I measured Manfred's arm he weighed 330 lbs. Priest weighed 230.
It would be helpful to know Ronnie's arm size at his various bodyweights.
Nothing can be proved without measuring.
Right before I measured Manfred I was speaking to a very, very famous bodybuilder who scoffed at the notion (and rumor) that Manfred's arm was 25"- saying they looked no bigger than 22"- and this was a man with decades of experience at the highest international experience. I was stunned that he would say what he said, but perceptions after all, prove nothing.