I realise its a long time since the last post here, but I found this article that explains exactly what you get when you option MagneRide suspension on your Mustang. I did and its fantastic...
No one answered your question. The answer is no the Steeda spring is actually a lot softer than the stock spring and therefore easier on your perch. But as others have said, just replace the spring and perch in one simple go and move on to your next mod.