You bought them through Troy when he worked at Westoaks. He is a fellow clubmember I've known for the past 20 years. I think I remember he saying he sold a few one side only sets. I faintly remember him asking me about selling them (one sides) to someone.
I wonder what the rate is of the short/weak side of the SS springs??? I wouldn't want more than 160-170.
I think right now it sits too high in the back. You could buy those drop front spring hangers from Dr Diff. But like was said that much rear arch is not great for handling. You get some "rear steer" when one side is compressed and the other is slightly extended when cornering hard.
Another way to go is the 1" or 0" arch MP circle track springs.