: So what exactly are we in disagreement about?

I don't think we are really in disagreement about anything. And it is not really you I am addressing with my comments. Over the years there have been many posts to this bulletin board asking about anthropometric measurements. The assumption of the these questions is usually that these measurements will produce an "optimum" kayak. I don't want people to go away thinking that just because they used body parts to measure that the boat will automatically be optimized. They should know that the fist beside their butt gives room to roll comfortably in a SOF, but it does'nt help at all for getting the displacement of the boat right. They need to know what the measurements provide and what they don't. If someone is particularly light or heavy, they should adjust the system accordingly.

If I seem fixated on displacement it is because displacment drives all other aspects of performance from stability and rollability to speed and sea handling, and that unless you actually weigh yourself nothing else can tell you what the displacement of your boat needs to be. While you can produce a good design while ignoring displacement, you can not produce the "best". I would also suggest that people would be better off taking measurements they fit in and like, than using a system of measurments for a boat they have never seen or tried. Unfortunately, I am in the business which often asks people to do just that, but what can I do. I would sell everyone displacement optimized designs, but I would have to charge a lot more.

I know the Greenlandic system doesn't predict displacement, so that is what I address. You know it does provide room for comfortable rolling, so that is what you address. If it seems like I am arguing with you I am sorry. I am just trying to get my point across and some times it is easier to state it in the context of what you say. And unfortunately my statements come off sounding negative.

I hope that between us people learn the limitations of the systems and learn what they need to know to successfully build themselves a kayak they will enjoy.