I wrapped my bd4 crossover pipes with ceramic tape from JC Whitney, to minimize heat conduction inside the cowl. I painted the engine white and the cowl interior black to maximize heat radiation to the cowl. The cowl exterior became noticeably hotter to the touch, so ideally you would use a conductive (i.e. no foam) cowl material. My Osprey cowl, made of polyester/fibreglass becomes quite plastic on the ground. Peter
It appears keeping the heat in the exhaust flow is the key.
