On an "E" I started with MP XHD springs. Ride height as new was a little high. With use, they dropped and it was a little low. Also spring rate seemed low vs beefed front T bars. Not balanced.

The fix was easy and not expensive. I had a local spring shop add one full leaf to the springs for $100 and change. This service got the ride height (+~1") and spring rate where it needed to be. Spring rates are approx:

stock: 120 lb/in
XHD: 140 lb/in
XHD + 1 full leaf: 170 lb/in