Luke - according to the specs listed at the bottom of the J/30 Class rules, there is a note that reads tip rounded to a centerline depth of 20mm maximum below Section V. To me that sounds like a curve with a radius just over 0.75". I'm thinking of cutting a section of PVC pipe lengthwise, lining it with release cloth, then filling with thickened epoxy to provide a uniform shape for bonding to the keel bottom.