I do it for two reason. One, I do believe corbina are line shy and two is less water resistence because of line diameter. I feel I get bit more with lighter line. I would rather get the fish on and worry about how to bring it in with the line test I am using than get bit less and have less worry about landing the fish. Most of the corbs in my area tend to be around one and a half to two and a half pounds and are a bunch of fun on 4# where if I was using 6#, I would have less concerns about being broken off. Of course if you tie into a shark, ray or butt, it gets real exciting and you better have a spare spool for your reel. That is also why I tend to use the same equipment I would use for trout. Probably the only difference would be sinker and hook size. Makes for a lot more fun with FISH ON! Besides, the ones we lose always tend to get bigger than the ones we land.