If using std shocks I would say no lower than 30mm (and even that will lower the life of the shockers quite a bit too), although I sell 4 shortened shocks and 4 lowering springs for £139 (40mm all round and should be fine with std anti roll bar)
I also advise to check the poundage of lowering springs or you can get super over stiff suspension (My kits are rated at 960kg front axle weight)