Most boats steer horribly in reverse, and the Springer seems to lead the pack. Mine has a left hand prop (viewed from astern), so the prop walk when going astern pulls the stern to the right. I find if I give it full left rudder before starting the motor astern, and give it 1/2 throttle astern, it will usually back straight. With a lot of practice I finally can steer it in reverse somewhat. But if it ever gets into a hard right turn it just spins, so I have to stop, go forward a bit, then go into reverse again.
After I had the boat for a year, I added the triangular piece (1/4" wide) to the rear of the rudder. This makes the boat turn more tightly going ahead, and seems to help with steering in reverse.
Has anyone had any success with adding keels, running strakes, or other underwater fixtures to help with backing?