Just finished my version of the denver chair, with a couple of mods.
Replaced the alloy spreader bar with a plastic covered chain, it doubles as a retainer when the chair is folded. Instead of the non slip strip down the support it has a small piece glued to the block under the seat, reversed the logic and saved buying a full strip. Added a large hand wheel ( salvaged from somewhere and just waiting for a use to arrive
) to the 3/8 coach bolt so it can clamp the side cheeks against the sides of the seat support.
Bill