Should a full size mattress fit in a pull behind camper?
Yes, as long as the camper is big enough. I once folded a full size mattress halfway and put it into a Honda CRV.
Regular mattress length ways or sideways/crossways? Pull behind camper would be no more than 8 foot, couple inches wide otherwise would have to have oversize permits like Mobile Homes. SO, figure minimum 6 inches less inside you would have about 7.5 foot interior space. Take off another foot for making bed and pillow space, getting in and out- figure 7 foot crossways by at least 10 foot unless a Tiny Tear drop based on old 4x8 box. a 16 foot is moderate pull behind length, maybe single axle yet. Mattress size- twin is 39x76 inches or 1 meter x1.9m some are the 39 x75. some camper come with Dorm size- 30 inchx75 or 30 inchx80 (basketball players size) I have a standard twni box spring and mattress in a 18 foot Holiday trailer fitted crossways up front, has walking room at foot of bed. I have another 30 foot or so before washroom wall narrows floor space- so a 42 inch wide standard mattress could be put in and a 60 inch wide queen would fit also. Long King at 66 wide x 84 long would be pushing limit to get in and out- have to get through narrow side doors. 7.5 foot wide by 10 foot single axle compact camper is a common 'small' hard camper and popup size. inner fender wells would mean narrower bed on floor or raised bed on top of fender wells. I have 42 inches between fender wells on 8 footer with roofing- I used a camp cot crossways for couple naps. , 7.5 x10 has 45 inches between wells- it is open utility trailer now but has hauled a queen box spring and mattress with some side space when loaded length ways. What size is the ACTUAL pull behind camper? Get out tape measure and see how much floor space or available side space if elevated, mattress size and door size. .