A 6:1 will dump just as fast as another 6:1. It's the same thing people.
I still believe a 5:1 is going to be the best thing for you. Also if you need a new mainsheet (remember you just increased the puchase), just tell your favorite rigger that you want a single braid. There's some really nice stuff out there, and the sailing world should branch out from the standard "lets put 3/8" sta-set on everything" attitude.
If you don't want to change the mainsheet, then splice on another 10 feet or however much you need in the next size smaller line.
Another way to get around buying a nother sheet is to make a pennant that attaches the mainsheet block to the boom. If you have a 1' pennant, you just reduced your mainsheet length by 5' (if you go with a 5:1). Really helps get the spaghetti out of the cockpit.
Merit 25 # 764 "Audrey"