I had exactly the same problem when I went to the 105. I found that even though I had rig forward, I pointed up wind.
In my case it was a combination of problems:
I was oversheeting with backhand, had too much weight in back foot and wasnt putting enough pressure through the mastfoot.
I also had my front arm bent. I discovered that if I tried to keep rig further away ie. straightened front arm, I wouldnt oversheet and the rig was naturally forward and I wouldnt point upwind straight away. I also stood a little more center of the board until I started moving up on to the plane.
As I am only fairly new to it all myself, these things may not be exactly correct but they did work for me.