Once we got the forestay, shrouds and mast butt in a comfortable spot for the conditions, I fine-tuned with the lever. If I needed to depower, I pulled on a lot of backstay, which tightened the forestay and made the jib flatter. Of course, that flattened the main. If I felt the main had become too flat, I used the lever to slide the mast aft, which deepened the main. Conversely, if I needed more power, I eased the backstay, which softened the forestay, powering up the jib. That also deepened the main, so I would lever the mast forward. That forced low bend in the mast and flattened the main. This “range” of adjustment was initially tough to correlate, but as we became more comfortable with the lever, we dialed everything in relatively quickly.
As I adjusted the lever, I gauged the mast position by looking at the space between the aft edge of the mast and the back of the partners. To further quantify that, we put a vertical mark on each side of the mast with a sharpie and then a peel and stick numbers scale on the deck on either side of the mast. That way, Jeff Eiber, our forward crew, could confirm the mast location. Once into the race, rarely did we keep the mast in the same upwind position for the entire race. Whenever the wind built or dropped off, we moved the mast.