I used to have lots of guns. But they were all lost in a tragic boating accident. Shame.
As far as the box, I was looking to have someone build a custom Cordura bag that would fit the bottom 3/4's of the frunk. The top quarter would have been reserved for "lay-in" items like personal electronics, wallet, keys, etc. My current plan is for a Bagster tank lid cover topped with a Tweety (small) tankbag for the personal valuables. The Frunk could then be filled with a 100% height custom bag with a grab handle on top.
I'm very sorry about your loss of firearms bemmer! If you need to talk about your loss, you have my #.
I can say this, because the same thing happened to me. It was a tragic event in my life!