Solidworks 2016-17 SE

I made the mistake of setting my mid point at (1) when I should have done it at (2). I'm too far gone to start over and trying to get it all to move is a trick in itself.

Now I have to learn to create custom planes in order to do the bottom part. Tried but can't figure this one out. How can I create a top plane simply 0.5 in below the original?