  We use a two-body, light-cone pion wave function (which vanishes when one of
the constituents carries all of the plus-momentum) to construct a double
distribution. We show that the resulting generalized parton distribution has
incorrect behavior at the crossover between kinematic regions. Furthermore the
positivity constraints are not respected. On the other hand, the
field-theoretic, two-body double distribution gives generalized parton
distributions that have physically correct crossover behavior and respect the
positivity constraints independent of the model wave function used. However,
the sum rule and polynomiality conditions cannot be satisfied with a two-body
wave function alone since Lorentz symmetry is not maintained.
