In all sets of experiments, we found that even small changes to force field parameters can profoundly affect the stability, cooperativity, and even the geometry of the helix. For example, the helical pitch could be tuned in a continuous manner by varying σ S . By varying the backbone angle equilibrium value by just 2.5 degrees, we observed a transition between two helices with different pitch, radius, and backbone native contact sequences. This type of insight hints at design pathways for switchable materials. In many cases we also determined the parameter bounds for achieving a stable helix. Features which prevented cooperative folding into helices included too weak of a backbone torsion force constant, too strong sidechain interactions (ε S ), too many residues, and angle values that deviated too far from those in the original helix model.