Cool. Good luck! Glad to see there's another nut out there crazy enough to attempt this.
Some notes on forming the bump: I tried several hole sizes in the 'forming' pipe. 7/8', 15/16', and 1". I'm not sure what an actual graflex bump measures, but 15/16" looked best to me. I used 1/2" hole for the 1/2" 'forming' bolt. Forming the bump stretches the metal, and the hole becomes oval shaped- so I drilled the hole out round again with a 9/16" bit, into which the tap worked well. I recommend trying all this with pipe scrap first. :)
Now that my daughter's saber is done, I spent some time on mine today.
I wrapped the bunny-ear arms around some 1" steel (same size as my blade), and made some collars that will wrap around the arms.
The idea is to clamp the whole thing in a vise. The collars and rod should help the arms keep their shape wile I turn the edges over with a hammer.
I may use a little heat, which will help the metal move where I want it to.
It takes a silly amount of custom '1-off' tooling to form these bunny ears. Again, I recommend just buying reproductions if the size works for you!