Frank when you build your box, put a wooden divider between the barrel and butt/action. Not just to keep them separate but also to reduce crushing possibilities for that 1/4" ply. Doesn't really need to be screwed or glued, but it can be.

Your Greener is a great gun. I was sorely tempted since I have recently bought a Greener hammerless from just about the same era (sold 1903, built 1901 or 2 as I recall). It would be nice to have a hammer and hammerless brace of similar guns.

_________
BrentD, (Professor - just for Stan)
=>/

[Linked Image from i.imgur.com]