"unless there is a physical stop" -- Leathermang

"The lower spring perch has a slight shape to it. The very end of the last coil is designed to rest against a small stop in a bit of a depression." --Brian

Ok,,, sorry to ask this next question... the springs have a top and bottom I think... either paint marks or closer coils or ground different...So you are sure they were installed in the correct orientation ? I know this bothers you because there are so few parts which could cause this... old blacksmiths are less bothered by this sort of stuff than Trained Engineers ...
I suggest you get the micrometer out for the spring wire size... remember the pages of specs posted when someone wanted to lower their car ?