Have you done the shallow water board alignment drills I've suggested?
Practice in water just deep enough to clear the fin....
You can learn to steer your board, from the mast foot, by pushing/pulling on the boom and inclining the sail in different ways.
After some practice you will be able to turn your board 360 deg. in either direction and stop it at the direction you want to go (slightly below a beam reach) in your water start.
When you can "steer" your board by rig pressure/boom pressure and rig inclinaton, then when you are in deeper water you do exactly the same things while flying your rig.
Now you can set the direction easily for your water start.
Get things all lined up, show a bit of the sail to the wind, push/throw your rig up and follow it onto the board.
I know, much easier said than done!
Hope this helps,