To demonstrate the capabilities of cg_openmm, we examined a 24 residue homo-oligomer system which we designed to fold into a helix. Guided by initial estimates for bonded parameters derived from a helical modeling tool included in cg_openmm, we systematically varied sets of force field parameters and investigated the effects on cooperativity and stability of the designed helix. Specifically, we varied the sidechain size and energetic Lennard-Jones parameters (Section 3.2), backbone angle and backbone torsion equilibrium values (Section 3.3), sidechain angle equilibrium value with fixed backbone equilibrium angle (Section 3.4), and backbone angle stiffness and backbone torsion stiffness (Section 3.5). In addition, we varied the number of residues using a set of force field parameters found to produce highly cooperative folding in the 24 residue model (Section 3.6).