I would go for closer to 44/56 front/rear percentage. You will want to fill the left side of the seat up with lead first for sure if you have a smaller driver. Don’t offset the seat too much to the left of you decide to move it. The center of gravity needs to be towards the center of the kart. Let me exaggerate to prove a point. You could mount the seat 6 inches further left and then mount all the weight on the right side of the kart bolted to the frame and the percentages will be “correct” but do you think it will handle well?