I would think you are correct about the 2K airtank not fitting in the shell correctly, but why not just buy a new nitefinder and practice on that. I mean the things are $5.00, and that's not really too bad. It's better than risking your masterpiece breaking.
I would write what barrel it fits in best. That has a lot of confusion too. Also MD foam is grey. And so is frost king. I would add those two brands. They both only fit in 17/32 and CPVC.
I have to disagree. Frost King foam fits in everything, Tight in CPVC, a bit loose in PETG, perfect fit in 17/32 brass, a bit tight in 9/16.
Very nice, but just one question. Why not making a pull-pin, or homemade nightfinder priming handle for it. My friend has had two lock n' loads and it isn't easy or comfortable priming them without a pull-pin.