dear John,
I will elaborate a bit on my display to provide you (and others) with inspiration for possibilities in " pickelhaube display" , mine is not perfect, but I like it very much for more than 10 years now.
ten years ago I made a design for my pickelhaube and mutze display, I demonstrated earlier, (a large cubboard with top shelves for my collection, consisting of 7 elements each able to contain about 9 headgear items). (some contain less to provide space for higher items with " trichter", parade plume or eagle (GdC).
at that time I really spend some time to think about the best solution to store them away from dust and mites, in an acceptable way for my spouse and kids, in the living room with good illumination and a minimalistic design to avoid hinges and lines from glass doors and frames.
each element is covered with a vertical glass plate that slides into place without hinges.
A carpenter made it, and I/m happy with it till today, although I regret it is not bigger (as the collection grows, the cubboard doen not), and it definitely has its restrictions, all others items (swords bayonets cuirasses uniforms don't fit in...), so they are largely stored in boxes...
(I made a similar but more simple display in our holiday house to be able to expand my headgear collection as a solution for that, and swords are allowed on display on the wall over there by my housemades...)
I hope it can serve as an inspiration to you and others,
have a nice weekend