Hi Roger: This is a tough question – one about which the data is sparse and that from manufacturers somewhat biased in one direction or the other. We are just finishing a book on heavy weather tactics (“Surviving the Storm”) in which we have a great deal of data on this subject. In general I think you can say the following: 1-Windage and/or hull area for waves to grab hold of is the first factor, rather than weight. These are typically size related, but not always. You could have a 35-foot cruising cat with a lot more windage than a 60-foot racing cat. 2-Once a wave has started to accelerate your vessel, the issue becomes displacement as it is the weight times speed which creates the load. The type of device which is appropriate is a far more complex question, one which is based on the structural integrity of your cat, the buoyancy of the hulls, and type of fins (i.e. if you have fixed keels or removable boards). The book will be out towards the end of November and we’ll be starting to post excerpts on setsail.com in the next week or ten days. Good Luck – Steve