I don't know how you "UV stabilize" polycarbonate, if it's something (like a dye) you add to it, or something you do to it.
It's an additive.
Polyamides are UV-opaque, but through absorption and not reflection. Absorbing UV rays excites the polymer molecules themselves, causing the polymer structure eventually to break down and lose structural strength. The internal fractures also cause opacity in the visible wavelength. Extended exposure to UV will, over time, break down polyamide materials.
UV stabilization additives, typically benzotriazole compounds, absorb UV directly but this is not the primary mechanism of stabilization. They also draw absorbed energy away from the polymer as thermal energy. This latter role works only if the compound is added to the polymer formulation prior to thermoforming.
Lest this seem too exotic, polyamide sold under the trade name Lexan is the material compact discs, DVDs, and Blu-Ray discs are made from. It's hardly an exotic material. The optical-grade version of Lexan is what the vast majority of "plastic" eyeglass lenses are made from. Opticians will tell you that they offer Lexan lenses with "UV protection," but they don't tell you it's an inherent property of the material. It's a very common substance. It just happens also to be what space helmets and space visors are made out of. However the helmets in
Apollo 13 and
From the Earth to the Moon are made from acrylic because George at Global Effects couldn't get his vacuum forming machine to work on polyamide.
