Here's my Memorial weekend project - basically took dimensions from
@Nutterbuster 's post and cloned it the best I could from scrap metal. I don't have a way to weld aluminum so it's solid steel, strength is overkill and its not super light, but the only thing I had to buy was the expanded metal for the top and it was a fun project. I coated the top with truck bed-liner to help with grip and she's super solid.
Next steps are straps and to figure out how to fit it into my system, ideally I'd like to attach it to my saddle so it will always be in the same place, no matter which climbing method I'm using.
If I pursued a second prototype, I would try to save weight by either finding someone who could weld aluminum or buy less beefy metal instead of compromising for what was laying around. I would also like to experiment with scooting the legs closer - although it may compromise some ability to handle side pressure, it would give me access to smaller trees to use.
I'll post a follow up after I get straps and do some yard runs, but overall I'm happy with it. I love this design because there are no moving parts, everything is stationary and like nutty says in the video, it doesn't creak. No bolts, all fully welded.