: The eye-shaped sprung (ala Bjorn Thomasson) one is simple to make,

OK, that made no sense so I Googled it and found it.

WOW! How stinking simple!! This is why I asked for ideas. I am waiting to see what others offer up but this looks like my next strongback to me!

What material did you use for the strongback? I am guessing it needs to be solid wood but plywood scarfed together would make a really rigid frame but I don't like the idea of driving screw into the side of the plywood.