In this paper we consider CIP 2 and OSIP 3 formed from small sheets (MeAlO)n(Me3Al)m (n = 6-7, m = 4-5) vs. larger sheets 16,6 and 26,9. The sheet 6,4 has a reactive OAlMe2 group and thus is analogous to 16,6 in forming ion-pairs 2 by methide abstraction (Scheme 2). Both ion-pairs feature a chelated counter-anion (see Supporting Information, Table S-1.xyz for structures). In contrast 7,5 and 26,9 react via [Me2Al] + abstraction and furnish OSIP 3b and 3d; these would be in equilibrium with CIP 2b and 2d through reversible dissociation of Me3Al (Scheme 2). In these two cases, many structures are possible for CIP 2. We located these by examining electrostatic potential maps (Supporting Information, Figures S-1 to S-3) of the corresponding sheet anion (usually one face is more electron rich than the other) and focusing on those O2AlMe2 groups with highest excess electron density. In practice, the [SBIZrMe] + cation was then placed above the most electron rich face within van der Waals contact with one or more these groups. The resulting stationary point might not be the lowest E isomer, but this would not change the conclusions, just serve to increase the height of the insertion barrier. The equilibria between 2 and 3 and neutral starting materials are important with respect to catalyst speciation prior to polymerization. We will discuss the energetics later in connection with modeling of catalyst activation behavior. The most important question is which of these ion-pairs 2 are the most reactive towards olefin insertion. This can be studied at M06-2X/TZVP level of theory, as in our previous study and other studies of olefin insertion. Ion-pairs 2 will be in preequilibrium with the corresponding π complexes 4 which can form via approach of monomer syn or anti to the counter-anion.