Once you've stubbed the wig, it's time to get creative!
With the extra support from the superstructure, your options for crazy ponytail styles are infinite. Here's just one example: Take the foamcore from my "poofy ponytail tutorial"
... and place it on top of the stub. It can be very narrow at the base, and it does not need to rest against the back of the head at all: The very tip of the bolt is enough to support even a thick, long ponytail that weighs a pound!
The ponytail will never sag because the headband on the inside of the wig acts as a counterweight.