Something to realize on the "don't turn backwards" issue. When a piston engine is shut off, it coasts to a stop against compression of one random cylinder. It also can spring back a bit, sometimes with force. Think of the loads on the chain at this point as the slack is instantly taken up.

Have a listen to a 90's Dodge diesel shutdown. Sometimes you hear the drive belt go scritch as the motor rotates backwards a bit and belt tension is applied to the spring loaded adjuster side.

This is far worse than manually and slowly rotating an engine backwards.