I'm having a hard time visioning exactly how you have a "head banger". But a simple attention getter would be to simply tape a length of knitting thread from the corners and let it dangle long enough, that even if you are looking down and not up, you'll see the thread and remember to stay clear of it.
I do the same thing with the slide outs and pool noodles. I cut the pool noodle long ways, then it slips over the edge of the slide out. Most folks put the pool noodles horizontal on the bottom. I put them vertical on the edge and let them hang down and extra 5 or 6 inches. This way, I can see them when not looking up, and if it do hit one with my head, it's soft.
I also have a wrap I put around the hitch king pin too. I've never banged into it, but my 9 years old grand son did once and really put a knot on the top of his head. Ever since, I've been wrapping it.
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2019 Montana High Country 375FL
2014 Chevy Silverado Duramax, 6.6L Dually