Thanks guys for the input. Seems that anywhere from the manual distance to the 1/2" to 1" measurements work. The airframe/pipe combo I'm using won't allow me to have the cone outside the pipe... SOOOOO, I decided to add a pipe support to my turbine test stand and see what I get. I ran the turbine with the max distance away from the pipe I can get (which also helps with the CG) all the way down to the 1" from the can that the manual describes. From a temperature standpoint there was no difference in pipe temp among the various distances. Warm at the tip of the pipe (not hot enough to burn my fingers) and cool at the bellmouth end. I have no way to measure thrust so don't know how the measurements affect that! The pic shows the farthest out of the pipe the airframe bulkheads allow me to position the turbine so I will go with that and see what happens...