Hybrid films of the nematic liquid crystal penthylcyanobiphenyl (5CB) on the surface of glycerol were studied in the presence of an in-plane electric field. In this geometry there is a macroscopic flexoelectric polarization P-f with a component in the film plane that couples linearly to the field. Here we report the electric field and film thickness dependence of the width of the 2 pi reorientations (2 pi walls) in the c director that are trapped by the field and interpret these observations based on continuum elastic theory. We find the difference between the flexoelectric coefficients to be e(1)-e(3) = + 11 pC/m.