Ever since I switched all planes to PULL - PULL with fishing line snugged up, There is no hint of flutter.

Most flutters are due to flexing pushrods in 1 direction. When they are pushing there is a real possibility that the wire can flex if not supported very well by the guide tube in the pushing direction.
In a highly loaded jet I would do PULL - PULL with the lightest, SS, braided, fishing leader.
You can put a short spring in the down wire to create tension during final crimping of the lines.

Pull - Pull also prevents servos from striping their gears for NO reason.
Flutter is not always heard when flying alone or with other planes.

Rich

Rich