Wilson Combat sent this out in an email and I thought it would be helpful to visitors here.
Getting the right length pad on your 1911 trigger helps mate your finger to your trigger so that you move the trigger straight back without disrupting the sights. Ideally, when you grip your 1911, the middle of the first pad of your trigger finger will naturally touch the trigger pad. If your finger touches the trigger closer to the joint, you probably need a longer trigger. If your finger touches the trigger closer to the tip (or you routinely wear gloves), you probably need a shorter trigger.