HOW to de-tune X650 to prevent freeflows

[Chocoholic]

This is from a DA Aquamaster post:

On the negative side,in extreme cold water you end up having to de-tune the X650 a bit to prevent freeflows in a face down position (since it does not have a coaxial exhaust valve and diaphragm).

So, HOW do I de-tune an X650 ? Can I detune it by messing with the breathing resistance knob or is this some kind of thing I have to have done by a regulator technician? I am seriously considering getting the Scubapro MK17/X650 (a late christmas gift for me).
Thanks,
Choco

 

[Al Mialkovsky]

Take it to a tec. It actually is kind of a simple thing but....take it to a tec

 

[Chocoholic]

Doesn't matter anymore, I got the MK17/S600 today.

 

[redacted]

Unless something is defective, you should be able to control a slight FF with the user adjustment knob on either of those 2nds.