Mine is yet a work in progress, here's where I'm at now but it's time to go to work. The piece is part of the inside cap of a 5ml juice bottle with child proof cap. Some metal will have to come off here but not much as I would like as it will reduce the number of threads as well.
Gonna have to square that area under the lip on the plastic also, that might just be the hardest part.
So here is the finished insulator.
At work I added a small washer to the firing button, this washer is the same OD as the part of the button where it passes in and out of the cap, this gave me 0.5 mm more travel on the button, that my not sound like much but considering this mod's button only has about a 1.5 mm throw so it's a huge improvement. This washer must be of perfect size as it will pass in and out through the center hole in the bottom cap(picture below).
With this bottom cap set up it now accommodates Panasonic CGR18650CH battery as well as the sony 30 amp 18650 and that is with the stock battery adjustment screw in the upper cap.
If I hadn't sanded the negative contact screw down some the MNKE 18650's would also work fine. One small washer and one piece of a juice cap is all thats needed parts wise.
Note that the washer I added to the button essentially makes the shaft of the button longer, not to be confused with simply putting a washer under the screw head, that would just raise the screw but shorten the throw.