Hi Mark. . .

Good Question and I will post our recommendations for all to read.

Happy New Year and the best to you and your family . . .

Distance measured from the outer nozzle to the entrance of the actual pipe is:
Super Bee: Minimum 20mm (3/4") / maximum 25mm (1")
Falcon: " 25mm ( 1" ) / " 31mm ( 1 1/4")
Super Eagle " 25mm ( 1" ) / " 31mm ( 1 1/4")
Rhino " 30mm ( 1 1/4") / " 38mm ( 1 1/2")

Additionally, we are finding through testing using installed ByPass assemblies, if you leave the top half (half toward you) of the ByPass off, each turbines performance increases quite nicely as compared to a completely enclosed ByPass. Just FYI. . .

Best regards,
Eric Clapp
Jet Central Micro Turbines
Lifetime Warranty
Jet Artes Gulf Coast
Skymaster ARF PLUS