One comment about Rope guards which some trawlers use ( a frame, coming
from fwd, attached to a plate which surrounds the prop) The plate
surrounding the prop can act, to a degree, like a Kort nozzle, in that
it will reduce "propwalk" to some degree.
G A Kort nozzle, for me, is proof that "propwalk" is, in the majority,
caused by the prop alone,as it turns, not how the "wash" hits the hull,
or reacts to it.

otn