Well, for sure you don't want to plan on having any straps that run outside to inside. If it rains, you will have water wicking in and dripping on your interior.
Maybe you could use bungie cords to hold a hammock up against the ceiling when not in use, if it is hung too tightly to pull to the side.
I had an ENO hung inside of my full size work van and didn't find it useable due to the hanging angles.
Good luck!
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