I know with my 2" spacer lift in the rear with the stock spring and the F150 levelers, that the spring didn't want to unseat when on the lift. The thing that kept the axle from dropping further was the upper track bar hitting the fuel skid (I haven't notched mine out). The track bar has hit the fuel skid every time when it's on the lift, even without the F150 levelers and the spacer lift. But I also have my rear sway bar connected too.

I believe with the rear sway connected and the upper trackbar contacting the fuel skid, that my spacer lift, stock rear springs with the F150 levelers should NOT unseat. I'm going on a offroad trip on Nov 12 so I'll know for sure then.