I remember many years ago when sailors were crossing the Pacific in heavy conditions they would sometimes trail a spare anchor rode from the centerline of the stern. This would slow the boat down a bit and add longitudinal stability, moderating a lot of the course deviation and taking pressure off the autopilot. The old salts who did this said it made the boat a lot more comfortable in heavy seas so they could get some rest. I have never needed this and don't know if it is still practiced but might be a worthwhile method to investigate. Anything to settle the boat and add stability when the waves are roiling all around in 40 kn of wind seems like a useful idea to consider.