I took a 14' SB down last year. You'll be able to take highly technical lines on all the big name rapids and avoid the big munchy holes (maybe except for Lava, though there may be a good route on the left for you), and you'll have an absolute blast on all the many many more rapids that no one talks about and the the 18' gearpigs just pass right over with a little bump in their ride.
Sounds like a great time to me!
Nothing in the world is more yielding and gentle than water. Yet it has no equal for conquering the resistant and tough. The flexible can overcome the unbending; the soft can overcome the hard. - Lao Tse