I use one pillow but analyze: what's the optimal pillow setup for MY needs? Map the pillow factors: height, firmness, material based on sleep position and neck issues. Calculate: if I optimized pillow stack (number, height, firmness), would neck pain and sleep improve? Show me the pillow prescription: this height and firmness for my position. Give me the testing method: how to determine optimal pillow setup. Include: whether one pillow is limiting me, optimal setup for my position, and whether to use multiple pillows.