I have a Hakase in jade green celluloid. It can accept a CON-70 but for a variety of reasons I am not the hugest fan of that converter, and the CON-40 is pretty lacking in ink capacity.
I have always liked the CON-20; they have good flow and filling and cleaning them is a breeze. Should I be worried about outgassing though if I leave one in a celluloid pen? I am not sure what the sac material is made out of but I know that sacs were known to cause discoloration in older colored celluloid pens, which seems particularly noticeable in green celluloid pens. With that said this celluloid stock is considerably more modern than what those pens were made of and possibly more stable. The color is absolutely stunning and although I assume if it were to discolor it would be many years down the line, I would rather mitigate this as much as possible.
Any thoughts on this would be most welcome!