A simple 2-dimensional model is introduced to study molecular stacking in planar-non-ionic chromonics. The model allows changes in aggregation, arising from changes in interaction regions within a chromonic molecule, to be quantified. Application of the model to a typical hydrophobic core - hydrophilic corona molecule, such as the triphenylene-based chromonic TP6EO2M, shows the energetically preferred stacking arrangement of molecules is dependent on the preferred inter-molecule separation and the relative sizes of the triphenylene core and poly(ethylene-glycol) corona. Further, we show a minimum aromatic core size is required to form chromonic phases, explaining why functionalised benzene rings do not form chromonic phases.