  When calculating the index of a minimal surface, the set of smooth functions
on a domain with compact support is the standard setting to describe admissible
variations. We show that the set of admissible variations can be widened in a
geometrically meaningful manner by considering the difference of area
functional, leading to a more general notion of index. This allows us to
produce explicit examples of destabilizing perturbations for the fundamental
Scherk surface and dihedral Enneper surfaces. In the case of dihedral Enneper
surfaces we show that both the classical and our modified index can be
explicitly determined.
