What you have there is a traditional cellar. 8ft ply sheets at 45oish plus a 1ft kickboard. Get it built.
the maths is that 8ft at 45 deg takes up 5.65ft and then add the kickboard of 1ft - 6'8" total - if your cellar is 6 ft high then do 50 deg plus 1 ft kick.
you could always have a tiny kickboard....
One or two old mattresses underneath completes the deal
yes it is worth it