I built one with a big old gate hinge out of plywood as a prototype. If it worked I was going to weld up a sturdy one. But it has held up for almost 3 years so I keep on using it as is.
HERE is a slide show on how I built it for under $20.
The Mustard Monster site has a bunch of ideas in the lower half of
THIS page
I like the Robust Solution for its quality and the fact that it swings down both to the front and to the rear. Keeping it out of the way in all hollowing circumstances. $342 isn't an awful price postpaid. My gate hinge solution swings down and back toward the headstock and it is well out of the way also. But it looks like the Robust solution gives you increased between center turning length. This might make my Elbo hollowing rig work too without an auxiliary post. My angle iron and gate hinge solution is'nt accurate enough for long spindle turning. I might upgrade to Robust if I can find some loose change!