Bob is right. If your mast step was in an aft position and your headstay was short, as you slide the step forward your headstay (if left unadjusted) will be even less able to span the now greater distance. Make sure your headstay is adjusted to class max. By my calculations 1/2" of forward movement at the step equates to ~3" of additional aft rake at the hounds. If the tuning guide is followed exactly, this in turn will yield 1) A tighter headstay 2) less prebend and 3) a consequently deeper and more powerful main. This will maximize your pointing ability and power the boat up in light air.
