I hear ya...I'm no shorty my self...long legged 6 ft 1...and likewise enjoy frittering my time away on little projects like this to save a few bucks...

And frankly I made my own set recently also, before changing course and going with the Sebring seats. Instead of that channel steel I just used 2 pieces of heavy gauge strap steel (might have been 3/8"? PLENTY solid), drilled the holes, and even took the time to put a weld-nut in 2 of the holes to simplify installation of the seats by integrating threaded holes. It worked, and was not that difficult. But then my 5 ft 4 inch wife sat down in the drivers seat couldn't get the seat forward enough to reach the pedals. Not good. So what I really needed was not just more legroom, but more range both directions. And I get great joy out of letting other people drive my car whenever I get a chance...my wife takes it out with a friend or two of hers sometimes, and I still say my favorite day as a FGF owner was cruising past the 15.5 year old kid down the street, and watching him light up with excitement when I stopped to ask him if we wants to go for a ride..."yes"...and then nearly seeing him crap his pants when I moved over to the passenger seat and handed him the keys (he was about 2 months into his drivers permit). And I don't think I ever felt more safe on the wrong side of the car in my life. Thank God he was relatively tall...he had to move the seat all the way forward and was still a little stretched out. If I had set it back any further he would have been in for a very serious and unintended letdown.

I quickly changed course and those extenders were only in the car for a couple weeks until I got the Sebring seats, modded them to fit, which now give HUGE range and satisfy anyone from 4 ft 9 to about 6 ft 6...in legroom AND height adjustments. Now I'm confident anyone can drive and I love that, not to mention modern comfort for cross country drives.

But as usual, I drift off topic. Those extenders I made got cut up and used for something else or I'd offer 'em to ya. But going back to your post #1, the raw material you seek is nothing special, and probably in stock at your local welding supply store, and you probably don't need to weld anything to make these...just cut, grind, and drill. Just ask to see their thinner gauge (1/8"?) channel or somewhat heavier gauge strap. Pick whatever you think is strong enough for application, but both would work fine. Just measure your tracks for width if you go channel, to make sure they'll fit inside. If you have basic metal working tools like a cut-off and/or angle grinder, plus a drill, and a tape measure, you can make these in whatever custom setback you want. Just realize every inch of setback takes away an inch of forward movement and hurts the short guy. Maybe a non-issue if you're the only driver.