My experience with my ODay 25 matched. When that fat rear end starts to immerse, the stern is lifted, and the rudder loses its grip on the water. Starts out with severe weather helm, then rounds up into the wind regardless. Really needs a deeper rudder to be able to hold course, but the rudder is already an inch or two below the keel with the center board up.
Pretty dry boat under most "almost knock-down" weather. Our mini-poodle used to love to put his face to windward up on the forward cockpit coaming. His ear flaps would lift and start to fly as the apparent wind picked up.
Fred W
Stuart Mariner 19 #4133 Sweet P - with a nice deep Ruddercraft kick-up rudder that gets rid of both weather helm and shallow water issues.