I would place the pipe's bellmouth lip 1/2" to 5/8" from the very end of the P-80SE's tailcone. You'll have plenty of cool air entering into the pipe too.


One more very important step is to be sure the pipe is aligned perfectly center to the turbine outlet.

You can check this by looking down the pipe and center your eye on the turbine wheel's inner rounded tailcone (you may need a flashlight) to see if the 3 outer hex screws are centered within the bellmouth, while your eye is still fixed in this position, look at the exit end of the pipe to be sure it's centered on the turbine's inner rounded tailcone (exit of the pipe is not lower or higher than the shaft nut).... shim the pipe or an end of the engine to get the desired centering.

A mis-aligned pipe will created a hotspot on one side of the pipe's interior... this could collapse the pipe in the worst circumstance.