Need Mattress measurements 2003 Star Craft 21rb

Yeah. I have measured mine from the outside....just the width and lenght of the fold down section and got 80" x 45". But when you fold it down it seems there could be more room. I've only ever owned a pop up though and want to purchase the correct mattress the first time.

i wonder if i contact starcraft if they could give me the dimensions.

thanks for all the help so far.