Nice Jim. I don't think I have seen the hardware configuration you have here, but it certainly works. 

I didn't have a name for mine until The Schwartz, and Pop Wing called them pinch rods back in 2012 or so. Anyhow not a new idea, but a very good idea. 

My very first ones were 2, 1/4" dowel rods, with a sharpened end on each side, held with rubber bands wrapped around them with just enough pressure to hold them so I could measure inside cross diagonals. Using, or making some better hardware just improves them.