In order to check to see if your berth is level, it should be pretty easy to remove the cushion and use a carpenter's level (a longer one is better than a shorter one). Raise it on the low end until the bubble is levelled, measure the height and then calculate the rise as a perecentage of the length of the level.
I am pretty confident that your berth should be level if the boat was sitting on her designed waterline and, if your berth is off level by 2 inches over only 72 inches, then your boat must be sitting very low in the stern (that would be 1 foot over 36 feet)! The only answer, as you are no doubt aware, is to take additional weight off the sterns and/or to add hull
extensions aft. But wow, raising the sterns 1 foot would require some pretty some gigantic modifications!