I have been looking at a few rods to answer some questions for another member of the forum. He has an 8 weight that when you look at the real rating as determined with the common cents system it actually a 5/6 wt. He also has a 5 wt. which is really a 6. As you can see, there are some real problems with the way manufacturers rate their products. This makes it pretty hard for us to put the right line on the rods we buy without making a couple of tries. This also makes the question of underlining or overlining kind of pointless because we may be doing that without meaning to anyway. This was all gone over in a couple of other threads but I think the recent questions I have seen and recieved deserve this being posted again. Here is the link to the common cents ratings for many rods.
If you google common cents system you can find pdf.'s that cover how to do it yourself in case your rod is not listed. I hope this helps someone.