Going out further will not necessarily help you. IMHO you have one of two issues...One issue could be that your boat is riding up on the mooring ball. This happens occasionally to any boat, anywhere. Typically it is in light winds and current where the boat is just kind of sitting on the water and floats up to the ball. If this is the problem you can do what others have suggested with pulling the ball in tight and balanced between the 2 hulls. Issue two could be caused if your bridle lines are coming from the cleat down the outside of the hull (instead of the inside of the hull). Then your line can get caught under the boat causing the ball to pull in close to the hull. This is not good for your bottom paint or the banging It is best to run the lines under the life line on the bow of the boat and then back to the same cleat. (We do not use the cleats on the crossbar but some people do.) Do this on both sides so you have a V shape with the bottom of the V attached to the mooring pennant and the two tops of the V going on the inside of the two hulls, under the lifeline, on top of the crossbar and back to the cleat it came from. Hard to explain in words but I've tried to attach a picture of how to do it.