Party Room would be your best bet
I've transfered over 10m using this method and here are some notes that I find most helpful
-Put in 1 rune plate each time
-If there are people around, DON'T DO IT, just switch worlds
-usually the rune plate falls in one of the first 3 balloons and is ALWAYS within 2 steps of the big table
-and you should do it at some awkward time of the day 10:00pm-5:30am
-watch out for random people logging on in the party room trying to steal your plates
Hope that helps,
Sharksfan