The hatch on the Harlock VJ 140 is on the bottom, and not the top This is why I am told that the engine should not be ran with the hatch off. Maybe it could be ran on the ground if the airplane was inverted and sitting in a plane carrier...so the radiant heat could escape upward. Also, the exhaust pipe is a single wall design. The turbine conversion instructions call for the grooving of the rear fuselage exit to form cooling vents around the exhaust pipe and the inner skin of the fuselage, When air is injested into the jet some of the air flows around the engine and out the vents. When the hatch is off the radiant heat goes upward into the rudder/elevator cavities and does not have any ram air forcing cooling around the engine and out the vents. The engine is just injesting air from the atmosphere and not through the model air inlets. Also, on the first VJ I painted the turbine bay and fuselage areas around the exhaust pipe with BVM ceramic paint. But I did not add any radiant heat protection to this area. The servo harness from the rudder and elevators was first ran through black nylon sleeving, then ran through a high temperature fiberglass sheath.. However, when the tail pipe collapsed this wiring was destroyed in seconds. However,this time I am running the rudder/elevator wires, first with the nylon sleeving, then through the Dreamworks cool tube, as they pass through the turbine bay.. Also, I will cover the cool tube and surrounding fulelage composite with one layer of Dreamworks ceramic blanket. Then cover everything with the Dreamworks gold high temperature tape in the turbine bay cavity. I hoping this will do it. And also, of course, will not remove the engine hatch.