We show that highly deformed modes essential for nuclear dynamics modeling can readily be included in the symplectic no-core shell model (Sp-NCSM) space. In particular, a prescription for constructing general deformed k-particle–k-hole (kp–kh) translationally invariant symplectic starting state configurations and symplectic excitations thereof in a fermion-based spherical harmonic oscillator basis is presented. This prescription is used to build the symplectic excitations over all possible as well as the most deformed configurations in ¹²C and ¹⁶O. The extent to which these configurations enter into low-lying states for these nuclei calculated within the framework of the no-core shell model with a realistic microscopic interaction is then determined. Typically, the addition of these and representations to the leading results grow the overall overlap with the no-core-shell-model eigenstates by 5–10% for a total of 85–90%. And most importantly, even with the addition of these higher-order particle–hole configurations, the dimensionality of the symplectic subspace constitutes a very small fraction of the conventional full no-core shell model space, which reaffirms the relevance of the Sp-NCSM scheme.