|> Do you mean to suggest that a proa does not ride well for its size?
|>
| That is exactly what I mean to suggest, though lacking any experience to compare the two it is only a gut feeling based on what I know of hull design.  The very nature of a double ender eliminates some of for and aft assymetery that has been developed improve ride.

Can you point to a source that suggests aft fullness reduces hobby horsing?

http://www.shuttleworthdesign.com/NESTalk.html

"As hull shapes improved tending towards more U shaped underbodies particularly aft, pitching still remained a problem, because the large width of the stern sections caused the sea to lift the sterns as the boat passed over the wave, driving the bow down. "

Fat aft hulls are a problem, as I understand it it seems. Thats why I like HP's skinny ones.

| This is not meant to be critical of the Harry Proa designs.

Nor is this reply meant to be critical of ANY other design. We have both looked at similar designs, for similar reasons. We both have suggested we don't know much about boats. Let's just all agree we are talking about what we think we know. I have no malice, I credit to you the same.

If that changes, we will call it out, ok?

|> Its a good question, field evidence has it that longer hulls pitch less, and here we seem to be talking longer in terms of 33%. But also the bow offset of proa hulls is likely to reduce that further. Besides there are hydrodynamic fixes for pitch and pitch oscillation, just because catamaran builders rarely make the effort to control pitch doesnt mean it cant be done

| To suggest that catamarans builders rarely make the effort to control pitch is absurd.   Pitch control has been the holy grail of good catamaran hull design since the days of Woody Brown. 
<snip>
| Unfortunately most commercially built cats are in many ways no optimal.  

I think you actually agree with this, right?

The link above suggests there have been 6 or 7 generations of hull design to get us to this point. So, lets just say the effort has not been as vigorous by some designers as others?

|  The hull designs you see today are the product of that effort.   There is no disputing the fact that longer hulls ride better, but the challenge is to achieve the best ride for the length you have to work with.

I will object here. Again, you can drop length as a constraint and put cost in its place. Then you can simplify this to 'How does one get the best ride per dollar.'

| Boat designs are full of compromises.  For example, I'm willing to accept the flat bottom of the KD 860 hull, which is less efficient than the round bottom of Sagitta, both for simplicity of building, and for greater load carrying, not to mention having the cabin sole closer to the bottom of the boat for a lower profile for the given draft. 

Boats can be compromises. But sometimes a design is just better, in that it better meets criteria across the board.

I suggest that people can argue bottom shapes all day, but the first order variable is length. That need to be acknowledged. Steal dollars from the expensive bottom shape, put them into length, and build the cheapest bottom, and you always win.

| The narrow bows, increasing in displacement fairly rapidly, and the transom sterns rather than double ender canoe sterns, are used BECAUSE they offer less pitching.

With all due respect, regarding sterns, this is the exact opposite of what I read from boat designers.

https://www.boatdesign.net/threads/v-shape-vs-flat-bottom-vs-round-shape.38088/

| The placement of the accommodations / widest hull portion is not an accident.  It's designed to concentrate the greatest weights at the optimal axis, which is close to the pitch axis.

Agreed; put center of mass over center of rotation, and cluster the mass around that point. But it does not have to be in the hulls.

|  My priorities are safety, payload, close windedness, a tolerable motion, and decent speed, as well as low initial and ongoing costs..... I'm sure I've forgotten something.

Does anyone not want all those priorities?

P.S.

Have you got a materials cost on the boats you are looking at? I know you are looking at putting two boats together, but have you got material costs for each, as a rough guide of expected costs? Or any cost projections?