  We present a hybrid combination of forward and inverse reconstruction methods
using multiple observations of a coronal mass ejection (CME) to derive the 3D
'true' Height-Time plots for individual CME components. We apply this hybrid
method to the components of the 31 Dec 2007 CME. This CME, observed clearly in
both the STEREO A and STEREO B COR2 white light coronagraphs, evolves
asymmetrically across the 15 solar radius field of view with in a span of three
hours. The method has two reconstruction steps. We fit a boundary envelope for
the potential 3D CME shape using a flux rope-type model oriented to best match
the observations. Using this forward model as a constraining envelope, we then
run an inverse reconstruction solving for the simplest underlying 3D electron
density distribution that can, when rendered, reproduce the observed
coronagraph data frames. We produce plots for each segment to establish the 3D
or "true" Height-Time plots for each center of mass as well as for the bulk CME
motion, and use these plots along with our derived density profiles to estimate
the CME asymmetric expansion rate.
