I manufactured an aluminium-bronze firewall passthrough for the thermocouple wires, P-leads, alternator and other sensor wires and installed it directly ahead of the EMS module. This time I made the passthrough hole large enough for all these wires and more, including an internal layer of firesleeve plus an outer firesleeve clamped over the extension (which has a bead machined at the front lip to stop the firesleeve slipping off).
Behind the firewall there's enough room for the 2" windshield defrost SCAT tube to pass up through a hole in the electrics bay. I'll cut this hole later, when I'm ready to install the two punkah louver vents as well.