Re: 2wt line on a 3wt rod?
Of course you can. It will change how the rod loads and casts, but I commonly over-line and under-line rods from 3 wts. up to 8 wts. depending on the type/size of flies I'm fishing, and the water I'm fishing. Most of the changes are very slight, and many anglers wouldn't even notice. As most are saying, try it out. If it feels too "stiff" or isn't loading enough for you, line up.