Older Mosquitos do not usually have the centreboard case at the maximum measurement from the bow (3353mm) and as a result need the mast more upright (sometimes even leaning forward).

Pretty well all Mozzies built in the last 10 years have the cases at the limit.

I have a small rope stopping the rudder but the real reason it's there is to stop the rudder box gouging holes in the transom.

I think Peter is right about starting gently with the tack and pushing the rudder over more as you get through the eye of the wind.
Another important point is to stay out on the trapeze as long as possible - until you think you have left it too late!
If you come off trap and then start the tack, the boat is very likely to stall half way through.