If you are using the "factory" jib and set up, and you were to set the head of the sail at a different (higher) angle on the mast you will change the sheeting angles at the clew which can alter the control and set of the jib i.e. if the angle of the jib sheet is higher then the direction of the "pull" on the sheet is more along the leech of the sail and less along the foot and less "even" through the sail, and you may find that the jib is much more difficult to set so that it works well with out "hooking" the leech, or, having too full an entry at the luff and thereby reducing your ability to point.