I used some leftover maple and plywood from Van's shipping crates to make the housing of the straightener. The maple was only about 3/8 thick, so I had to glue several layers together.

Here's an in-progress image of the lower roller housing before the other tall side plate is glued on. You can see that there will be three rollers on the bottom.

Side plate glued, and rollers installed.

The top block has T nuts top and bottom for the jack screw. Normally you wouldn't use two T nuts in this arrangement, but I was hoping there would be some binding on the jack screw causing it to act as a locknut. Turns out it worked perfectly.

The jack screw started it's life as a carriage bolt, but I cut the head off with a die grinder leaving just the square part to wrench on.

Here's the completed tubing straightener. It came out pretty well. Let's see if it works.

Hah! This thing rocks! I couldn't stop laughing when I tried it out. Very cool. The tubing isn't perfectly straight like extrusion, but it's definitely better than I can do by hand and it's really fast to use. And it was pretty cheap, too. $17 for the casters, and another $17 in hardware. Sure beats the $200 version.