That looks much better than what it looks like in my C
XLR Thunderbolt.
Absolutely a better design than ours!
Here's what we did today. 4" foam on the ends and 2" foam in the middle. Because we are old, LOL, we bought a queen size mattress for a topper!
Just got our 2018 36TI5 and it lays flat as well. There is some little plastic brackets that are on the sides that "supposed" to lock the folding part in place may make sure that they are unlocked all the way they could be holding the middle up
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Mark and Tina
2018 XLR 36TI5
2009 Chevy 2500HD