I'm not sure what "front to back" instead of side to side means. Do you have any info or articles on how you do this?
Managing the balls energy and how it slows down when it reads the pattern. You want the ball to slow down appropriately and have the right amount of energy at the break-point. To me, if the ball floats thru the heads I know it's going to make a quicker move off the spot (this is key later in the block on flat patterns) and if the ball is slowing quicker I know the ball won't be as jerky and give me a smoother motion (this is KEY on flat patterns when they're fresh) that I'm looking for.
On a THS, you can get away with left-to-right reading often (this is a horrible habit though).
EDIT: Sorry for the off-topic response OP, but I think todvan asked a good question very few understand.