See my 2nd post back .... after you mentioning your problems on gently rolling dips in the road and then thinking about what's probably going on ....the soft mode of the Koni FSD shocks may not play well with the "long throw" of coil springs when going over (the low frequency of) gently rolling dips in the road.
My stock Ford front shocks are working well with the front coils, almost complimenting the rear Koni FSDs as they interact with the short throw rear leaf springs. What amazes me - and the reason I asked about a possible lifetime warranty on stock Ford E450 shocks - is that the stock front shocks are still damping well after nearly 70K miles. So ... assuming that the stock E450 front shocks are fairly stiff as compared to the stock shocks on lighter vehicles ... I may replace them with Biltstein HDs to go along with the dual-mode Koni FSDs in the rear.