The leading part of the M-theory low-energy effective action has been conjectured to be the minimal supersymmetric completion of curvature-to-the-fourth corrections to the eleven-dimensional supergravity action. This fact is difficult to exploit, because a component Noether procedure would have an infinite number of steps of ever-higher order in the curvature expansion, and any 11D, N=1 superspace will put the theory on-shell. In this talk, I will describe a program to build an 11D, N<1 supergeometry that appears to be “off shell enough” to supersymmetrize the leading M-theory corrections to the eleven-dimensional supergravity action.