  We investigate parametrizations required to reproduce observed Fermi surfaces
of overdoped and slightly underdoped LSCO in two different models. One is the
standard three-band saddle-point slave boson (SB). The other is a model of CuO4
`molecules' randomly tiled in the plane, emphasizing the distinction between
the local overlap, always the full (bare) one, and the effective overlap,
connected with the reduced bandwidth due to the random tiling (RT). We conclude
this distinction is physically significant for underdoped, but not for
overdoped LSCO. This is consistent with the observed open Fermi surfaces being
due to correlation effects.
