This is all very confusing.

Using a jetCat 120sx with a Smaller Bellmouth (as one that comes with Skymaster kits) I was told to measure from the end of the rear exhaust of the turbine to the front of the Bellmouth and keep the space at 3/4 's of an inch.

From what I read here it appears that the larger Bellmouths are set up differently.

Bottom line is it all depends.

Stan