on low balls, i have better feeling using only the rotation leverages of the arm, with the elbow attached to the side.
At upper levels, i use different leverages because i can't bring the elbow attached so much to my side..
here coach Kyril explains a fluid top spin forehand , using trunk rotation, arm rotation onto the shoulder joint, and forearm rotation.
the perfect point of contact seems to be placed between the knees and the waist... I think this can be defined as a low contact point.
Impossible to me to hit with the elbow attached to the side on high forehands.