Engine shutdown problem

Hi 

The reasoning behind the shutting down of one ignition first, wait, and then the other is to avoid backfire in the exhaust.  

In shutting off one side while at idle speed it will allow the engine to drop a small amount of RPM.  This in turn cools the mixture in the head and when we turn off the second one it should stop without any problems.  If we simply cut both ignitions there may be enough speed at idle to try to continue to run for a few more turns which can cause a backfire in the exhaust.   The propeller loading when we shut down with only one will help the engine stop without trying to run past the next compression cycles of the pistons, or at least less of them. 

Cheers