Well, I resolved my 450mm lens need.
Picked up a Nikkor 450/9 and 240/5.6
but only the 240 is in a shutter. The
450 came in a Sinar DB.
So now what I need are two things
1) A pair of inner cell caps to protect them when rotating cells around.
2) A box for storing cells when not in use. Though I did briefly consider
dismantling the Sinar DB mount so that the threaded center could be used
to store the cells safely ... but that depends on how much it's worth.
Box should hold the 240/5.6 since the 450 cells are quite small.
2.1) An option would be a barrel that holds Copal 3-mount cells.