Nose Wheel Steering effectivity...help!

Hi everybody!I have a bit of a problem: I'm working on a 737 flight model but seem to have too little nose wheel steering effectivity.The problem manifests itself when taking off with a crosswind of about 10-15 knots or more. I'm unable to keep the plane on the runway, even with full rudder deflection. When accelerating through about 100 knots, you notice that the rudder becomes aerodynamically effective, and I start to regain control, but by that time I'm ploughing through several parked aircraft and terminal buildings..... :)So this phenomenon, plus the fact that when airborne, it behaves perfectly in crosswind, sideslip and engine-out situations, leads me to believe that it is a lack of nose wheel steering effectivity.(To clarify, this is a full-size home-built cockpit with rudder pedals and a yoke, and I know it flies pretty well in the air because I'm a 737NG pilot in real life)Can somebody please give me some pointers as to how I can increase nose wheel steering effectivity without messing with the rest of the rudder characteristics? I've been looking at the .air file with AirEd and know the .cfg file pretty well, but can't seem to put my finger on this.All help is appreciated!!Iz