This is the age old problem with lowering springs: You get the drop you get, and you can't adjust it.
If there's any settling at all, it's more likely to be at all 4 corners than just the rear. So you'll still be stuck with OTT rake.
Two options.
1) try and get hold of some rear springs and adjusters from a coilover kit. You'll be able to tweak the rear ride height to match the front. Problem with this though is that you're mixing and matching spring rates, and if you go too low at the back, your dampers might not last very long.
2) Try and get a refund on the Apex springs, and go for a more tried and tested spring kit, like H&R or Eibach. Of the two, Eibach are also a tiny bit rakey, but not to the point where it looks odd. H&R give more of a level stance. Both kits drop around 30mm.