  We present first results of a program to study the dynamics of undisturbed
bulgeless, low surface density disk galaxies in order to probe the underlying
structure of dark matter halos. High resolution H-alpha rotation curves are
combined with optical and infrared imaging to place strong limits on the halo
profiles. We find noticable variation in the shapes of the rotation curves, in
contrast to previous claims. The implied density profiles are still
significantly more shallow than profiles derived from most N-body simulations;
unlike previous HI observations, beam-smearing cannot significantly affect this
result. Based upon stellar mass profiles derived from K' band observations, we
derive the angular momentum distribution of the stellar disk and find it to be
broader than that of a uniformly rotating solid-body sphere, but remarkably
consistent from galaxy-to-galaxy. Finally, based upon K' band surface
brightness profiles, we find that low surface density disks must be
significantly sub-maximal. Furthermore, maximal disk fits based upon Modified
Newtonian Dynamics (MOND) have maximum mass-to-light ratios which are too small
to be consistent with stellar population models; without the ability to
significantly adjust inclination angles or infrared mass-to-light ratios, this
sample presents great difficulties for MOND.
