  Break-up fragmentation patterns together with kinetic and configurational
energy fluctuations are investigated in the framework of a microcanonical model
with fragment degrees of freedom over a broad excitation energy range. As far
as fragment partitioning is approximately preserved, energy fluctuations are
found to be rather insensitive to both the way in which the freeze-out volume
is constrained and the trajectory followed by the system in the excitation
energy - freeze-out volume space. Due to hard-core repulsion, the freeze-out
volume is found to be populated un-uniformly, its highly depleted core giving
the source a bubble-like structure. The most probable localization of the
largest fragments in the freeze-out volume may be inferred experimentally from
their kinematic properties, largely dictated by Coulomb repulsion.
