In reply to The_flying_climber:
The vertical and horizontal 2x4 will be very (probably too) highly stressed and if it collapses you'll be hurt. At the very least they need to be solidly built triangles with very little left cantilevered out at the vertices and big enough to maintain stability even if you make dynamic movements near the top. The legs on the floor are in your landing area so need padding.
The hole plates serve no purpose, the tension members are all you need to adjust the angle, chain backed up by rope works well as would ratchet straps or a little hand winch. A friend of mine has this exact design (on chain, no plates and installed in a shed rather than supported by 2x4 triangles). In a few configurations it needs a stick wedging in behind it to reduce the wobble but generally it's stabilised by its/your weight. On his the top of the top panel runs in garage door style runners across the ceiling so it can't fully collapse on you but it's not absolutely necessary for stability.
Personally I'd keep it simple, flat boards pivoted at the floor and supported cheaply with a disposable/adjustable frame in compression (can use lighter, cheaper timber) that wedges into whatever garage/room you have available.
Lightly frame the panels to keep weight down, a little flex will be no problem. Spacing the frame off a couple of inches to make better use of structure rather than mass of material will dramatically improve the stiffness to weight ratio for very little extra work.
Ultimately, if you're handy enough to draw and build that you'll figure out the problems and solutions as you go. Good luck
jk