Propulsion steering issues

Your rudder is just a flat plate ? You could rivet on a couple of wedges to see it that does the trick. You get two bites at the cherry, at the leading edge, and again at the trailing edge.

 

Yes rudder is just a simple flat plate

so simple wedges installed in the area colored in red will make make a difference?

Not too worried about steering resistance as I can add a longer handle to the stick steering lever to compensate

 

I think so, but just try temporary attachments first, that way you can try more aggressive or less aggressive wedges, or you may find it has an unexpected effect you don't like anyway. But when you put the helm over, it seems certain to increase the effect .