Your point-on distance will increase with a shorter arrow, due to the change in your sight picture. In addition, your actual arrow trajectory may change because your arrow weight will be different with the shorter arrow, and your shorter arrow may need to be re-tuned for your bow slightly.
All you have to do is shoot some arrows and see where they are hitting. I'm sure after about an hour on the range, you'll have the new distances correlated with the location of the arrow point in your peripheral vision. I've made similar adjustments, as I tend to play around with arrow weights, etc., and it's not very hard to do.