For me the 3 most important parts of any seat is the rail height, distance to the last ladder rung, the ability to turn and take a shot from the side. From what I have read most people spend 2 hrs max in a seat.
How we sit is not how we shoot, you need the ability to change from the long period sitting back into a shooting position. 99% of estate seats I have sat in the rail height is to low and being left handed they are set on the rides for the cursed right handed people lol...
There is a very good chance who ever is reading this is sitting down in a seat they use every day, plus a number will have a cushion some where in that seat lol.
The best example I have worked my seats off are school/collage chairs with lots of research has been put into there design as they have to work for a huge range of people.
For a few pounds you can sit in a seat work out the right height and build your box around you, I always tip the seat back a bit because when you build it you wont be trying it with all you winter kit on. It is surprising how much a few extra layers will push you forward.
With most steel seats the rail has some form of adjustment, that is not very practicable in timber so to take full advantage of a wider ark then once you have found the right height I would use it all round.
Keeping a steady rest for the one chance you might get all day is top of my list so with my seats I worked the size so I can jam myself against the seat frame.
With ladder/legs/braces the angles in steel is easy to produce, free standing seats need a good foot print so the angles are compound. Bolting off steel plates set at the right angle would be my way forward...
Tim.243