  By studying the non-linear effects of overlapping instanton pairs we address
difficulties in the identification of instanton distributions when the average
instanton size is comparable to the average distance. For the exact charge two
solution, we study how its parametrisation relates to a description in terms of
individual instantons. There exist two dual sets of parameters describing the
same charge two instanton solution. This duality implies the existence of a
minimal separation between two instantons. Conventionally used lattice
instanton finder algorithms based on the assumption of diluteness tend to
underestimate instanton sizes. Finally we numerically confirm this for
realistic parameters of the instanton liquid. The effect is enhanced by
parallel orientation in group space.
