Ah, excellent points, thank you all! I was thinking about trying to stack some kind of additional washer under the center post. I have three 28mm Tobhs, two (black, copper) are definitely Tobecco, stainless probably is. The two mods are both authentic. I sent Allan de Silva a message on Facebook asking for some pointers, will post back here if I get any new information.
I also have a no name 22mm Tobh which had a post that was too long for the 4NINE. All three of my 28mm are too short in the 2SIX. It works (I guess) with a magnet on top of the battery, but I read that neodymium is not a good conductor so I thought I'd ask for other ideas.
That solder idea is definitely interesting, can you grind solder down?
I did loosen the contact screw to see if I could get any extra length out of it, but it does hold in the center post. Free tip: don't work with your hands over your lap, when things drop you spend 20 minutes under your desk looking for washers.
