Most of the Ford springs are linear or don't have enough rating to be decent (i.e. B's in some applications). I like the Progressive rates (like Eibach's) because I personally feel they are less harsh if they use decent rates. When a car has a 2" drop, it sucks when it feels like riding a rigid frame bike.
We should note that I'm older than most here and dont generally tolerate misery like I did as a kid.
Have you checked your spring isolators?
Have you checked your Control arm bushings?
Did you try loosening the rear suspension bolts puting the rear axle on jack stands to load the suspension then torque all bolts to specs and see if that does anything???
My isolators were old so I used a rubber mat cut out the circles and sanded down so they would be lower and not make noise.
I was on Summit Racing earlier and saw some Intrax lowering springs, INT-30-1-006. They are a progressive rate with a 2" drop. The only thing is they take a while to ship, I think. They are also purple powder coated if that matters.
I didn't know they still made those for Mustangs. My Intrax springs are yellow powdercoated, installed by the previous owner years ago. They dropped the car 2", and the ride isn't that rough since I put in the Tokicos all around. No sagging either. Gigiddy gigiddy.
Here's the lowdown on which H&R springs you've got:
Black - Sport
Blue - Super Sport
Red - Race
White - Super Race
I have the red Race springs and they are rated at 750/850 on the fronts. The Race and Sport give the least drop. The Super Sport springs will drop you a good 2" and very noticeable compared to race/sport springs. That's too low for me, though.
H&R is supposed to be great quality, so maybe there is something going on with your isolators, LCA's, and/or bushings. I've got all new control arms in the rear now (replaced the front A arms a year ago) and my stance is perfect all around (but didn't notice it being bad before either).
Most of the Ford springs are linear or don't have enough rating to be decent (i.e. B's in some applications). I like the Progressive rates (like Eibach's) because I personally feel they are less harsh if they use decent rates. When a car has a 2" drop, it sucks when it feels like riding a rigid frame bike.
We should note that I'm older than most here and dont generally tolerate misery like I did as a kid.
You may be older than most but I'm probably older than you. The FRPP M5400-A drop was about 1" and yes they are stiffer than stock (progressive?) but they are great at speed.