  High resolution low angle x-ray data are reported for the gel phase of DPPC
lipid bilayers, extending the previous q range of 1.0 {\AA}-1 to 1.3 {\AA}-1,
and employing a new technique to obtain more accurate intensities and form
factors |F(q)| for the highest orders of diffraction. Combined with previous
wide angle x-ray and volumetric data, a space filling model is employed to
obtain gel phase structure at a mesoscopic level. A new conclusion from this
analysis is that the hydrocarbon chains from opposing monolayers are
mini-interdigitated; this would help explain the previously well-established
result that the opposing monolayers are strongly coupled with respect to their
chain tilt directions. Even more detailed structural features are described
that have not been obtained from experiment but that could, in principle, be
obtained from simulations that would first be validated by agreement with the
wide angle and the new low angle |F(q)| x-ray data.
