I would be very interested to hear from anyone that has actually tached their engine with and without the deflector.

So far the thread has indicated zero decrease to 1500RPM drop when using a deflector.

I would suppose it may well vary depending on what engine, exhaust and possibly what prop you are using.

I see props for the OS55AX range from 13 x 4 to 10 x 10.

Unfortunately I dont have a Tach to check my OS46AX and OS55AX.