G'day Tubby, just been following the conversation with the other bloke who spells his name funny . Geoff and I have had a couple of conversations and I have a similar set up to him, Evernew van 22'6" semi off road and ARB springs and OME sport shocks. One thing I did do to start with, on ARB's advice, was have 400kg springs on the rear but I found this to be very uncomfortable with little or no load and sat the back up too high, so, went to 200kgs no lift and this is much better. If I need a bit more I will fit polyairs to the rear springs, but I know ARB don't endorse them and prefer to use a higher capacity spring, which is fine if you have the van on the back all the time but crap (my opinion) without. I have found the 200kg a good compromise for me and the boss.
I would agree with everything that Geoff (still find it hard to spell his name) has suggested in his above posts.
Cheers mate and good hunting, haggle hard at ARB or anywhere else you go.
The REAL Jeff