Does anyone (Hi Nick!) know what the dimensions and especially the gauge of the square metal tube Nick used in his forms video?
It looks like it's 4" x 4" (100mm x 100mm) but what gauge/thickness? weight? cost? (I think a 20' 16 gauge 4x4 is about $60 in Los Angeles)
Any thoughts on going heavier or lighter than what was used in the video.

I think square mild steel tubing is the way I'd like to go. For an old carpenter/cabinetmaker I found it frustrating and difficult making a satisfying strong back from 1/2" apple core ply.
Usually I can cut out sides in this stuff, rabbet a couple of edges with a router, then slap'em together and get perfect 90 degree sides. Somehow making a strongback wasn't so easy.
I wasn't satisfied with its straightness until I finally clamped it to a length of very heavy steel channel before screwing and gluing.

Nick sure makes it look easy. Probably the most humbling part of Nick's videos is that he doesn't have a 100,000 square foot shop filled with Computer controlled
Swedish machines.

Thanks

Will