Blends of nylon 6 and a silsesquioxane additive, aminopropyl isobutyl POSS (APOSS) were prepared containing 0–5% POSS by weight. APOSS was previously demonstrated by us to be an ineffectual additive at concentrations of more than approximately 3% by weight, lacking solubility and favorable interactions with the polymer matrix. Significant reinforcement was only obtained under the extreme confinement and orientation conditions induced by melt-spinning, under which it was suggested the APOSS might undergo forced-assembly into elongated, rebar-like reinforcement structures.