Lefty Kreh made the 50% rule for leaders and I use it all the time. A 9ft leader is kind of standard. There is a very simple formula, the one made by Lefty. 4+2+1+2=9 4.5+6+3+1.5+3=13.5 We start with 50 and taper down to 15. We start 4ft of 50lb, 2ft of 30lb, 1ft of 25lb then double the last distance of 2ft of 15lb. Listen to me walk through it or here’s a video where I explain it:

https://www.youtube.com/watch?v=q8vEd7NY53E