Looks good, but I have questions........
I need to build a steady rest for my 20" WWII-era lathe, so I'm currently gathering ideas.
1.) I wasn't planning to go with anything as heavy as 3" x 3/8" tubing

I was thinking 2" x 3/16", maybe 2" x 1/4". What is the reasoning behind such heavy tubing?
2.) I am planning to hinge the top half of mine. Should make loading parts a little easier. Any particular reason why you did not?
3.) It looks like the fingers have brass pads pressed in, correct?
4.) Can we see some pics of the base and shots of the steady rest sitting on the lathe with the carriage out of the way?
Andrew