What kind of performance are you getting? Are you porpoising, or just not getting the speed and ride you expect. Motor height can have a huge effect on your hulls efficiency, especially on a hull that's made to run at speed. I think the thingamajiggy to which you refer is the cavitation plate or more correctly the anti-ventilation plate. That does seem low but you'll need to get feedback from someone who really knows. From what i've learned here, I believe Seacraft hulls are more commonly rigged with the cavitation plate above the keel an inch or so. But keep in mind that the 233 is a pure deep-v with 24 deg deadrise or thereabouts,so rigging may require different height setting. While you wait for an answer from one of the resident wizards, you might check out
www.thehulltruth.com -- a lot of Formula 233 experience over there. Good luck!