We have an older (1983) OVNI Sonate 28. We have noticed a tendency for this model to "squat" in the stern when full power is applied to the diesel engine. The stern sinks down enough that water enters the transom scuppers and covers about a third of the aft portion of the cockpit floor. This condition does not happen under sail alone at the same hull speeds, so I suspect that it is a condition of where the sails apply motive power as opposed to where the prop applies it. I'm wondering if this condition is a normal one for this model? Any Comments?