My fly rod says 5/6 wt, and the instructions tell that it can be used with lines of both weight classes if I make the proper adjustments to my cast. My question is what would these adjustments be?
Your rod will take longer to unload and shoot the line under these conditions, giving the line more time to fall. Since the extra line weight will cause your rod to behave as if it has a "slower action," you will need to slow down a bit and open your cast as well as cast higher on back cast.
The magnitude of the effect will depend on the he rods listed action (slow, medium, fast) and the difference in line weight.