Excellent choice for helmet stands. I use them as well. The best fit I have found so far are bargain store martini glasses turned upside down. The base is almost exactly the size of a spike base retaining plate. Takes the weight off of the visors for a minimal investment.
Oh don’t you worry, I’ve very careful when displaying items. I only let sunlight hit on occasion usually when the weather is nice, which isn’t often here in the PNW
As I mentioned, I love the glasses for keeping weight off of the visors and really love the labels. I think all collectors are closet museum curators. Suggestion if I may would be to somehow remove the barcode off of the plywood. With a nice display like this I would hate to have attention drawn away from the goodies