Hi Crafty Fox,
160 lbs. is not HEAVY!..... in fact it's very light for an adult male windsurfer.
The average is normally around 180 lbs-185 lbs. (81-84 Kg.)
So, the issue is not your weight.
What board did they put you on?
I would have to say that their technique is realy not good.
If you need to get the nose of the board downwind, to get underway, that is something you
do with sail angle....not tipping the rig forward.
As far as your front foot, yes, you need to have it in front of the mast foot, but ONLY when you are in the process of uphauling.
Once the sail is uphauled and and you mast is held in your front hand, you need to get your front froot behind the mast foot BEFORE you even put your back hand on the boom to begin to sheet in.
Try bringing the mast across the board in front of your front shoulder (AFTER you have moved your front foot behind the mast foot) until it balances on the mast foot.
THEN sheet in very slowly and gently.
Your board will move off nicely straight across the wind if you pay attention to your "T" position alignnment.
You CANNOT really sail a windsurfer very successfully with your front foot IN FRONT of the mast foot.
You front leg and the mast will always be vying for the same space.
Move your front foot back BEFORE you even think about adding any power to the sail.