You are right about the 07 13M...
As for the 08 13M, I would guess the comfortable top end is right around 25. Slightly less than the 06 waroo 12M. But thats no big deal because if it's a solid 20 you will be on the 9m anyway!
Don't forget,if you buy the 13M and decide you don't like it, there is a 30 day no questions asked refund or exchange option.
Best will then resell it as a used kite at which time I will promptly snatch it up
You really can't loose... Best isn't gonna leave you hanging as long as you don't sit on it for a month before you decide.