I haven't seen any other threads other than the video itself... maybe I should go look to try and get ideas.

If you want to reuse the same coil on all calibers that will depend on what you shoot. Something really fat will require a different coil than vs a 223 or something. Also the coil gets hot over time. I don't know the limit yet, but you definitely want more than one coil. If things start getting really hot then just swap out a new one.

I ordered a bunch of 10 gauge solid copper wire and some of the heat resistant sheathing. I got enough to do at least a dozen or more coils. The sheathing is not required but it is nice to have. When I get the stuff delivered I will make some more coils.

Like I said above, the difference between 3.75 seconds and 4 seconds is not enough to matter (in my opinion), especially if you fine tune your coil size.

As far as having a long shell holder, I though about that but it would need to be wide enough not to tip over. I bought aluminum ones and they work great. The only issue I have so far is the one for 6 ARC sits a little deeper than I would like. It was made for a different taller cartridge than the ARC. It's fine for a reloading tray but specifically for this kind of annealing it would be nice for the cases to sit up a little higher. The guy that made them said he would make a custom one for me, but no telling when that will happen.