my suggestion would be to practice unlipping from both sides at all positions. Unclipping is like any brain-muscle action, practice creates neural pathways that will be more readily accessed if you have practiced the action. Knowing you CAN unclip from the right side (or whatever side is less natural to you) doesn't translate to getting your brain to make your muscles do so quickly, but if you practice unclipping from both legs at all positions and gradually increase the speed at which you do so, you will become proficient in stopping quickly and unclipping from either side regardless of where your foot is at the time. Simply practice. Basic life stuff. By the time you have become proficient you will also hopefully realize you be riding in such a manner as to never need that skill, but it's a good skill to have cause you never know when a moose or bear is going to pop out onto the road or trail.