I should make plain first what purpose this is intended for. This is intended to cover the back of my head during full intention sparring but where back of head blows are rare. From watching international tournaments, where there seems to be a large number of back of heads blows following wild and uncontrolled explosive actions (particularly in Longsword) I would have to say this isn't intended for that environment. In that situation wrapping your head in a full encompassing protector makes sense.
So, I bought a SPES Vectir a while ago but it isn't compatible with Leon Paul masks and when I adapted it still wasn't satisfied with the large gaps left at the top and sides when you are moving around. Unlike "normal" fencing masks Leon Paul masks don't have a large wire bar thing at the top for it to attach to.
I've looked over various more complete head protectors but I've been reluctant to purchase anything like this basically because one of the joys of fencing masks is that they ventilate really well. Wrapping your mask in an insulating layer of leather and padding strikes me as a really bad idea, especially when my practice doesn't justify it 99% of the time. They also they seem to restrict your head movement, side/side and up/down, which I would find really annoying.
So, to solve my problems I need something that:
1. Provides comprehensive protection to the back of my head to very occasional accidental impact without having to wrap my mask in a giant blanket
2. Attaches to a Leon Paul mask
My design is pretty simple really, it's a hardened leather shell which attaches at the top of the mask by a thin velcro strip into the existing velcro strap and at the bottom with a thin elastic cord under the chin. The shape follows the contours of the head and I've put leather "tabs" at the top and side that slide into the mask to ensure it overlaps where it joins the mask. Finally, there's a small thin piece of padding directly behind where it rests on the plastic head strap.
So far it works pretty well. It's light weight and doesn't appear to hold any heat. Aesthetically it looks quite good as well as looking quite minimalist. I've smacked myself on the head quite hard with different weapons: it certainly takes the edge off and holds up quite well. Finally, as I move around it doesn't seem to open up and expose any gaps so I guess I'm quite happy.
Already I'm looking to make a few tweaks, mainly to put the elastic chin strap around the outside of the back so that it'll improve things by pushing the tabs into the mask, at the moment being on the inside it pushes them out a little when in place. I also might add an articulated plate to cover the base of my neck.