If these are for the same fence you needed the forged tapers for, you are way overthinking this.
How many do you need? If its less than ten or so, just lay em out with a tape measure and a center punch. Takes less time than all this chin wagging about jigs.
Welding square bar thru square holes in channel is a pretty modern, cheap way to mass produce fence panels, but its based in mig welding from the bottom, where the weld wont show, and it fills the gap ofsloppy oversized punching.
commercially, you can buy the prepunched bar.
stuff like this
https://www.tsdistributors.com/store/p/714-Square-Hole-2-x-1-x-1/8-Bar-Channel.aspx
its not what you use for high end fencing.
just lay out the holes, punch em, and weld em.
do edwards ironworkers have a creep mode for the punch, so you can register on a center punch mark?
(edit- looks like they dont. You get what you pay for, i guess. Better ironworkers have a setting where you can creep the punch down and it will stop when you take you foot off the pedal. This allows you to register the punch on the center punch dimple, then punch the hole. Looks like edwards is like a mechanical ironworker- you hit the pedal, and it cycles, period.)