triptronic fluid change amount

[mountainman]

Getting ready to order the stuff to do a filter and fluid change on the 04 boxster and wondered how much fluid everyone has actually been able to drain out and replace. I have read the capacity in several publications and also noted that all is not supposed to drain out with the trans in the car. Also see where some drain it, refill and then drain and refill again because all does not drain out. Is this really necessary? Have slightly less than 80,000 on it, but look forward to putting about 12K to 15K more miles on this summer so thought I would go ahead and get it done now.