A. Stability and wetted area are critically important performance parameters, but it is not reasonable or practical to ask yacht owners to declare appropriate values for them. The 6 underbody types displayed on the CRF rating application work indirectly as surrogates for stability (via related keel volume, VCB and VCG), and more directly for wetted area. In addition, the various underbody type options help account for the advantages of a high aspect ratio fin keel with a separated spade rudder over a lower aspect ratio configurations, including a full keel with an attached rudder.