Kevin,
I don't know about the trim F86. My BVM sabre is being converted using the BVM conversion kit with full bypass. I havn't finished it yet and have not run the engine in the model. I can't see why there would be any difference with bypass or not. perhaps some of the more experienced modelers can answer. The back of the bypass is painted with BVM heatshield inside.

I suppose if the dimension from the turbine to the tailpipe is specificly indicated there must be a reason for it being so.

Regards

Tom Watson
Sydney Australia