Looking for some advice about what pound test to use for surf fishing rigs. I grew up fishing on a boat and have only been surf fishing for a few years, so having to worry about break-offs and working with heavy line, etc. is still pretty new to me. I tie my own rigs, generally in 15-20 lb. fluorocarbon. I tend to fish in close and don't really try to do any power casting and these have always done OK for me. The problem I'm having now is that my son is getting older and stronger and likes to really bomb it out there. He is starting to break off his rig more and more often when casting. I am using 20lb. test mono for the main line, connected to a 40 lb. test mono shock leader, which is then connected to a fluoro rig on the end. The knots are not failing; when there is a failure, it's coming a few inches below the knot connecting the rig to a barrel swivel(shock leader is on the other side of the swivel). We generally do not fish using heavy weights- 1-2 oz. is normal, every once in a while we go to 3 oz.
My thinking is that since it's the line that's failing rather than my knot system, I need to use heavier line for my rigs. Do I need to follow the 10-pounds-of-test-per-ounce-of-sinker-weight rule of thumb for the rig too?