Here we see that the the pRabi(500,2) results are an upper bound to both the pRabi(500,10) and Rabi-FCI-10 results, which again suggests an incomplete photonic Fock space. However, unlike the pPF and PF-FCI results we have examined so far, the pRabi and Rabi-FCI results are indistinguishable in the limit of a complete photonic Fock space. This is consistent with the proposition that the projected bilinear coupling operator agrees with the exact counterpart in a given orbital basis as long as it is projected onto a complete many-electron subspace.