I am building a frame fixture using 8020 and some simple machined parts. This is based on my learnings from the simpler one that I built, plus inspiration from photos of the Arctos Jig.

My fixture has these design goals:
* Flexible so that it can be used for oddball bikes (cargo bikes, tandems, etc)
* Breaks down into small linear sections for storage
* Cheaper than a used Nortac or similar jig. It looks like my total cost will be about $300 and ~20 hours of machine time.
* Not annoying to use, but also not designed to be very quick to dial in like most professional jigs. I have no plans to become a professional framebuilder and don't mind spending 30-45 minutes setting up a jig.
* My first jig was too adjustable, which made it easy to get things off of the centerline. On this one I fixed the centerline at 2.5" and am machining parts accurately so that I don't need to make them adjustable.

I'm highly influenced by the Arctos jig since that had a lot of design similarities (with much nicer execution) to my first jig. The rear triangle dummy axle is going to be a complete ripoff of the Arctos since I never came up with a design that I liked before. The Arctos is much slicker when it comes to setting angles.