When I originally posted about the seat structure, I left the seat adjustment separate from the main seat structure design. I had the ideas about how to implement the adjuster, but it needed some time to let them mature into a practical design.
The idea is to use the simplest adjustment mechanism possible. It needs to be set-and-forget, so the seat height doesn't change when you lift it up, but also be easy to adjust, so that means no fiddly mechanism and adjusting it shouldn't need tools. Low parts count and low weight is important too and there shouldn't be any extra hardware/fastenings if possible (i.e. I don't want to use car seat style lever and slide mechanism).
Seat adjuster assembly
Seat adjuster parts
Cross-bar connection detail
Adjuster bar clip
Unsupported seat length
The seat adjuster uses the sloped back of the side support as the control surface for the seat back so, because it is to all be operated by hand, any pinch points needs to be removed or protected. There needs to be no sharp/pointed/serrated edges that could catch loose clothing or skin --- especially because opening and closing the seat is to be a normal process for using the luggage space.
The end of the adjuster beam is rounded, as it is a moving structure that sticks out. The radius on the beam where the support locates to minimise the risk of pinching anything when the seat settles back. The horizontal gap between the seat and support means it shouldn't be able to trap anything between the two.
The adjuster bar clips/unclips to the seat back which holds it in place, while allowing easy adjustment (the removable bar is simpler than having a captive, sliding motion).
Like with the previous lattice hinges work, I've been doing some calculations for integrated elastic clips for laser cutting --- I'll be publishing more details on these soon.
Having a long distance between the support positions, which means they are only supporting point loads (and no bending moments), this length allows for a natural shock adsorption as part of the seat design. One downside of this layout however, is that it's not possible to adjust the seat with anyone sitting in it, you'd have to get out to readjust.