Thanks for the reply's
The OS .46 is the VFR, not the fan engine. What size pipe? I've seen reference to the 6.5 and 7.5 pipes. Is there a way to measure the pipe to determine which one I have? I've got two of these .46's and two pipes but am not sure of the size.
On the MVVS Do you have a formula for determining the rpm range via the pipe length? I'm wondering if a non-silenced pipe would be advantageous vs. the MVVS silencer?
Thanks again, this is really helpful.

Chris