Glad you found something that works. Most folks use swimming pool noodles, cut them in half and you have 2 pieces. Cut them once, long way. Pull one end apart and simply slide them over the edge of the slide-out.
I use to put them on the bottom of the slide, but I found out they work better if they are put in the vertical position. When it rains, they don't fall off. And if they are just an inch or two dangling below the slide, it gets your attention when walking around them more. Plus, the part hanging low may brush your head, preventing from banging it. Pool noodles are really cheap, can be bought at any Dollar General and work very well for this application.
Not in this photo, but I made a pool noodle cover for my fifth wheel king pin hitch also. My grandson bangs his head on it.
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About the time everything starts going well, something else breaks!
2019 Montana High Country 375FL
2014 Chevy Duramax HD 6.6 - 3500 Diesel Dully Long bed Crew Cab