I often rehearse a 6 day st. 6 week, and until recently, I had read that rule to mean that the 2 extra hours was the vote. Recently I realized that the vote is actually more about the actors approving the theatre to use a full week of straight 6's and that the 2 hours is the "luxary" that the theatre is provided for doing so.
It's one of those funny rules that's annoying to read, because it can sound like so many different things. I definitely agree, Sarah, that it's best to try and get the fittings into the rehearsal hours if possible instead of having to deal with this rule.
But I am wondering, is this how others are reading the rule too? "The actors by vote have to approve the theatre's use of 6 straight six rehearsals in a week, and by doing so, they allow the theatre to have 2 additional hours for costume fittings". This means that there are 2 votes for straight sixes, one for the use of them in general (in comb. with regular days) and one for doing only straight sixes in a week.