Finally got the OMEs and the Seikel front springs on my camper at the weekend. New top ball joints as well. It's now riding nice and level and a fair bit higher than the old saggy ones. The front is definitely quite firm – but not uncomfortably so – but have only driven a little so not tested thoroughly but will be loading it up for a weekend camp this weekend so all good. Only took me 18 months or so!
I can see what you mean about the rear springs being tight in the centre coils but they seem fine really. Those front ones really are very heavy gauge, I can see how a Doka would be hopping around a bit.