here are a couple options, open up the stock rudder with a file (which i think weakens it), ditch the stock rudder and use a transom pick up ( much better water flow), as for getting your trim strait, are you familiar with prop modding at all? sounds like you need to spoon out the tips of your blades a bit so that the thrust is directed in a more concentrated cone, I use to have that problem with one of the bigger props i ran in the past