Hi Steve, That will be the best source for ratings but my experience is that a Hobie 18 is noticeably faster than an F-27 in light air. That comes from experience so the only thing you can do is get some and then adjust the handicaps based on your actual results. If you will only rate one race then you should just stick to the published ratings. If this is for a club's entire racing season then you have lots of ratings possibilities. Just hope for medium or stronger wind because the light wind ratings really favor the beach cats, especially against the heavier tris. The F-28R, for example, is lighter than the F-27 and does much better in light air, but I would still prefer a beach cat in round the buoys racing to win on corrected time. Once the breeze comes up a little then the ratings are more fair and if it is really breezy then the tris start to have an advantage.

Just keep it light (hearted) and emphasize the novelty and fun factor of mixing the classes. Emphasize the experience rather than the results! Good luck,

Mike