I decided to design a bypass system for the cabin heat to keep the hot air from heating the firewall and tunnel area when not in use (heat valves closed). I am using 2" Y valves that were available from ACS. This will allow me to dump the heat from the muffs overboard before it gets to the firewall.
I used a piece of 063 aluminumsheet for the mount. It bolts to the sump at the aft two bolts. The mount it bent around the Y and riveted in 4 places. A layer of high temp RTV was applied between the Y and the mount prior to riveting.
Most time today was spent determining the location of the valve.