If stopping the engine on the mags is so bad for it, what about some of the very old a/c such as the Tiger Moth that doesn't have a mixture control and is always stopped by switching off the mags.
I appreciate that this has to be done after a 30 second "idle" but is there a damage risk here?
Waiting for the a/c to run out of fuel is the only other option to stop something of this vintage!!