I made several modifications to my SE5A, but by far, the most significant improvement was the addition of ailerons. I've only flown mine indoors so my flying space is confined. I first flew the SE5A without ailerons (rudder only) and while it was Ok, control and flight speed weren't what I was hoping for. I then added ailerons to just the bottom wing. With ailerons on the bottom wing I was able to flatten the plane in turns with opposite aileron. This allowed the plane to slow right down and was a real joy to fly. But control was still a little mushy so I then added ailerons to the top wing also. Now the SE5A has much better control.
I've attached a few pictures of my set up. Sorry for the poor picture quality.