  The sensitivity of nucleon-nucleus elastic scattering observables to the
off-shell structure of nucleon-nucleon t-matrices, derived from realistic NN
potentials, is investigated within the context of a full-folding model based on
the impulse approximation. Our study uses recently developed NN potential
models, which describe a subset of the NN data base with a $\chi^2$ per datum
$\sim$1, which means that the NN t-matrices are essentially on-shell
equivalent. We calculate proton-nucleus elastic scattering observables for
$^{16}$O, $^{40}$Ca, and $^{208}$Pb between 100 and 200 MeV laboratory energy.
We find that the elastic scattering observables are insensitive to off-shell
differences of the employed NN t-matrices. A more detailed investigation of the
scattering equation and the optical potential as given in a factorized
approximation reveals that the elastic scattering observables do not sample the
NN t-matrices very far off-shell where they exhibit differences.
