I wish you the very best of luck SC.
I have been fighting a loosing war with the ocean rats for a couple of years now. Oh, I win the occasional battle but every time I think I have the upper hand, they out smart me. Perhaps not out smart, they just stay away until they have worked out the weakness of my current
strategy and swop on it and exploit the weakness.
At one stage, I thought I had them beat. Boat all covered up with netting and all - took an hour to set it up and another hour to remove it. Two hours out of the day's sail
Left the boat for 2 or 3 weeks and they found a way to enter the netting and then moved as the netting kept away other predators. Those couple of weeks were enough to build a nest and lay eggs.... Grr.
I suggest you keep moving the owl around as often as possible as they soon realize it isn't a threat if it doesn't move and they seem to take great pride of sitting on it's head!
One idea I haven't tried is to get a store dummy dressed up and leave it in the cockpit!
Again good luck and let us know if something works!