Re: Backing Strength?
It depends on what you are fishing for and where you are fishing.
For open water or sand beach with no piers, pilings, rocks etc., coral, lighter backing, more of it.
If channels through coral or rock, barnicle/muscle studded mangroves, oyster bars, hard-bottom flats etc., heavy backing and less of it, or high strength spectra.
20 and 30# backing will pop like cheap sewing thread way, way under it's breaking strength when sliding over obstacles.