Thanks for your observations on short seat bottom, side folding, and balance. By the way I see an all iTrek manual is available now at
https://media.hobie.com/digital_assets/ ... l_2021.pdf although seems more basic and pictographic than in years past.
I have experience on similar watercraft that may or may not offer ideas. I recently got a similar looking chair with short seat depth. I think I posted here using a no-back pfd to create space. They do have a pad behind head but tend to have no pockets. Next thing I was gonna try is a SeaEagle inflatable seat, because with backless pfd the horizontal frame bit can dig in my back over long periods.
On tricky side folding, I have that problem on many inflato craft. Recently I have success by over-aggressively pulling in just the short bit of sides I can reach while straddling an end, Then I fold or roll and while pinned it relaxes just about into the right position while I step to the next part and over-pull again.
On stability for the larger size, I have several long boards with 39"ish width. Only one feels really non tippy to me, which is nearly a no-pedal clone of the iTrek 11. A major brand, not a rip off, but anyway the huge side cells give massive stability. Mine is "defective" in the sense of having a twist apparently from not attaching the sides cells evenly. Note to Hobie who might have containers of twisted iT11 rejects, this looks bad but hardly seems to affect performance. Maybe remove the Hobie badges and sell for half price