As far as your corners going unplanted, when you switched to hydraulic drive you need to use a jump start switch.  Ground drive knows you are moving because the ground drives the meters.  Hydraulic uses the speed, most likely from your GPS, and it takes a moment to decide you are moving, and not getting a phantom movement in the GPS.  The jump start switch makes it start when you push the button, and you hold it until you are up to speed.  You can also use a wheel speed sensor to try to gain faster engagement, but the jump start switch works better, at least for us.

This situation will also hold true for stopping in the middle of the field.  If you just take off, there will be a gap before it starts to plant.  Jump start switch fixed it for us.