I used to do a side thing... found that occasionally my whistle would be against my cheek and that I would only get half the sound coming out of the whistle. Half of a Fox 40 is still enough but I had people tell me that it sounded kind-a sick. Now I do center only. Mick are you telling me that I look funny with my whistle in the middle? Thanks!
I do have to remove my whistle as I talk to players (like talking to the post players while I'm Lead) but I also get noticed there (not necessarily looking funny but being heard) because I now get better volume when I speak. My comments are directed at the offending players without any impediment (whistle). Also less chance of inadvertant whistle while I'm talking because it isn't in my mouth. Works well.