Like you can see in my signature, I have the same combinations like you have, except for the IS133, I have the Ultrasonic. I weigh the same like you.
I still want to replace my IS122 for the newer IS110 (both 75 wide).
I can highly recommend you the Ultrasonic. It starts planing much easier and it will handle your 9.6 very well.
Furthermore, it will be much easier to point upwind in marginal conditions c/w the IS133.
I've been on other 85 wide slalom boards (Fanatic Falcons). Like you say, they are more technical to get them planing and once you get them planing they are pretty fast, especially downwind (typical PWA slalom courses). Upwind, the Ultrasonic performs far better and it is much easier to get into the rear footstrap.
If you're not concerned about speed and you don't need to win a downwind slalom race, but you do want to maximize the light wind days, the ultrasonic is really the best board you can buy.
IS87 / IS101 / IS122 / US147
Last edited by BelSkorpio; 17th February 2014 at 10:48 AM.