We decided to install wide slots in the glare shield with special lovers which spread the warm defrost/defog air over the entire windshield. Stratford and Dee especially were used to Cessnas with a short slot on the left which did a poor job of defogging or defrosting for the pilot. and nothing for the copilot. So, we installed a plenum on the bottom of the glare shield which tied the left and right defrost/defog slots together. As you can see these slots are fed from the two SCAT ducts from the "real" heater below. When we designed this system we had our original Subaru 3.6L engine with, of course, liquid coolant. That meant we had a "true" heater core which other builders reported produced a huge volume of heated air. After we switched to the Lycoming O-360-A1A engine, the heater core and fan came out. The detail of the "new" heat/defrost/defog system you can find under "Heat and Defrost" sections of this builders log.