I don't have the equipment to make metal fabrications, so I take inventory of my needs first then check around and see what I have that fits the bill. This bottom of this jig is made from leftover flooring from twenty years ago and as you can see 3/8" dowels,(same size drilled hook and lead weight holes). Also I made a backing plate from the same stock that I made several pertinent holes in it that can accomodate an 1/8" metal rod for stabibilty. The rod keeps the plug from moving laterally while I run the plug through the table saw blade. I generally make a cut 9/16" in depth for the bottom lip and 1/4" for the top lip and then cut off what I don't need for the top slope of then plug in question. Its simple, inexpensive, and works surpisingly well. Well here is my little gem.

I love jigs and the like -- very cool.

I have a similar jig that I devised from this website. I will encorporate some of your features in mine. Thanks