Well I got the job done, with nothing heat treated. I used 3/16" drill rod, 'cause 1/8" was universally suspected (or deemed) too tight.
The drill rod is dimpled, the holes have an embarrassing amount of skew (they were _supposed_ to be parallel!), and the whole thing looks like it was made by Joe the Neanderthal Machinist. But it works!
And while I appreciate the pointers from those who suggested I _spend money_ doing this -- where's the fun in that? If I wanted to _buy_ stuff I'd go get an ARF from Brodak
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and go fly. Honestly, what do you think I'm here for? To actually get something done in a timely manner? Jeeze.