There is no point in arguing about the ability of a boat to carry a dinghy on the cabin roof. You can estimate the boat's stability by measuring the roll period. The roll period is the time in seconds it takes to roll from one extreme to the other and back again. A properly designed trawler will have a roll period roughly equivalent to the beam in feet divided by three. If the roll period is too short, the boat will feel stiff and uncomfortable in rough weather and may jar the fillings from your teeth. If too long, you will wonder if it is ever coming back when hit by a wake. If the roll period with the dinghy on top is much longer than the optimum, there is too much weight up high, or not enough weight below. Roll period can be easily observed by sailing for a while in a beam sea with 3 to 4 foot waves or, alternatively having a couple of fat guys jump up and down on a side deck until the boat starts to rock. To accurately measure a boat's stability, ask any racing sailor or consult Skene's "Elements of Yacht Design." It ain't brain surgery. Larry Z