I had to add air bags to my EX to overcome the soccer mom springs Ford put in, and I have been very happy with the results. Thought about a spring swap (X code I think) but didn't want any lift/height added to it. Seems to barely fit in a lot of the parking garages in the area with only an inch or 2 to spare.
My understanding is the rear springs are fairly soft on the Excursion, and these exact ones are now 13 years old. I'd talk to a suspension shop about just replacing them with some that have a little higher spring rate.
A & A parents of DD 2005, DS1 2007, DS2 2009 2011 Suburban 2500 6.0L 3.73 pulling 2011 Heartland North Trail 28BRS 2017 Subaru Outback 3.6R 2x 2023 Chevrolet Bolt EUV (Gray and Black Twins)