I have a 40 ft trunk cabin with a queen size.
We have a queen memory foam mattress that fits but it has to be slightly compressed to fit between the built in "night stands".
83 x 58 inches is what I measure. Its probably 57 between the stands.
We sleep with our feet under the overhang and heads forward so it works fine.
Mystic,Ct. /New Port Richey,Fl