  The influence of broken structural homology, and the implied broken dynamical
homology, is examined for the Fundamental Plane (FP). A bisector method of
linear regression was applied, in 3-dimensions, to derive the best FP and a
bootstrapping procedure has been used to estimate the associated uncertainties.
For 25 E and S0 Virgo galaxies, the `standard' FP, constructed using R^{1/4}
model parameters for the effective radii (R_{e,4}) and the mean surface
brightness within this radius (Sigma_{e,4}) and using central velocity
dispersion measurements (sigma_0), gave a relation described by
R_{e,4}~sigma_{0}^{1.10+/-0.14}Sigma_{e,4}^{-0.55+/-0.09}. Using Sersic R^{1/n}
light profile model parameters and the computed velocity dispersion within an
aperture of infinite radius (sigma_{tot,n}) gave an `improved' FP described by
the relation R_{e,n}~sigma_{tot,n}^{1.37+/-0.16}Sigma_{e,n}^{-0.76+/-0.05}.
Upon removal of the known S0 galaxies from the sample, the above planes were
observed to change to R_{e,4}~sigma_{0}^{1.19+/-0.21}Sigma_{e,4}^{-0.60+/-0.11}
and R_{e,n}~sigma_{tot,n}^{1.72+/-0.24}Sigma_{e,n}^{-0.74+/-0.09}. The
perpendicular rms residuals about these planes are 0.084 and 0.050 dex,
respectively. A similar analysis of the Fornax cluster produced a FP given by
the relation R_{e,n}~sigma_{tot,n}^{2.03+/-0.78}Sigma_{e,n}^{-1.07+/-0.30}, in
tantalizing agreement with the plane expected from the virial theorem, but with
discouragingly large errors due to the small sample size of only 7. Similarly
to Virgo, the perpendicular rms residuals about this plane is 0.050 dex. A
Virgo-Fornax distance modulus was computed using Working-Hotelling confidence
bands. The `standard' FP parameters gave a value of 0.45+/-0.16 mag, where as
the `improved' FP parameters gave a value of 0.25+/-0.12 mag.
