Sea fishing, seeking recommendations for main line and subline~~

Alas, I am also strange, the question is not there, huh, a sentence to summarize it, do not want to type, say the main thing is that the line is thicker it does not matter, but the sub line do not and the main line is too much difference, up to a difference of one number, for example, the main line of No. 6, with a sub line of No. 5 on the line. You don't have to be blinkered, the sea fishing on how big the fish may be, so if you open the boat can be thin, but the dam is best thicker, the No. 6