Help stop the cast

Hi Guys.
I am in between the 3rd and 4th lesson with my local pro. Things have gone well and he's polished my setup, takeaway and finish. The problem is my downswing casts pretty badly. My old swing compensated so I can square the face, but I'm leaking power as you might expect. The last two lessons have focused mostly on this problem, but I'm still doing it. Habits are hard to break...

Does anyone have any advice? I'd love to use an effective unwind and not my arms so much to try and generate power.

Thanks very much.

Previously I used to cast the club reasonably badly but recently things although not perfect do seem to have become a lot better. I'm no expert by all I focus on now during my swing is from the top of the backswing locking my arms and solely turning my chest back around again towards the target, I find this a great feeling to visualise during my swing.

BE RELAXED! that is the greatest tip IMHO you can give any amateur. your grip should be so light that the club is actually heavy and hard to bring to the top so you have to swing your shoulders to get the club up there. then the club should fall into the correct path and you can't cast it. that is why heavy clubs help people, the club is so heavy that it jsut falls into place and it can't be casted. so the trick is to become so relaxed with you light clubs that it feels "heavy" and is imposible to cast if you are that relaxed.

A thing I used to do to help get the club "heavy" is grip overlaping with 2 fingers or even a real dramatic change 3 fingers. Slow you swing down enough that you can control it with 3 finger overlap (onlythe thumb and pointer of right hand on shaft) and it is real hard to cast it. HTH