In theory, I don't believe that mis-matching the suspension front to back should have any effect on the 50/50 split. The wheels should all turn at the same speed regardless of where your suspension is set.
To put it into perspective, think about suspension travel while driving, for example. Even being completely independent suspension travel for each wheel, just like almost all automobiles are doing now, the tires all continue to turn at the same speed.
As for lowering the front, I *think* that by lowering it, it should actually put more weight/down pressure on the front wheels, because it will be further from the flipping backward point, which should in turn help with traction and stability.
On the other hand, I could be wrong...lol, but with trying to keep the laws of physics in mind, I think that is basically how it should work. I haven't ever tested the theory, so I can't say from experience.
Of course, if anyone has any experience with it or if anyone has a difference of opinion, please feel free to share!!