Bumble, are you referring to 2012 season or 2013 season?
In 2012 game, a massive number of fans at the Roosters v Souths game were Souths fans. I would say your 65% figure was pretty bloody accurate.
However in 2013 it was probably closer to 30% at most. Easts fans massively outnumbered Souths fans for this seasons opener.
I have to say, I was flabbergasted, but I was at both games and this season Roosters fans were in a massive majority.
Same with the Anzac game that has traditionally seen us outnumbered at home. In previous years Roosters fans were well under 50% of the total crowd, but this year the crowd was 60% - 40% in our favour at the WORST. At best it was 70% v 30% in favour of Easts fans