The more important factor to consider than actual length of the rods, especially when mixing rands at different lengths is the distance to the point where the rod really begins to bend. I recommend you stick with the same action in a rod, for a diver medium-fast to fast action is best. You can get into trouble when mixing actions. If you pair a fast action 8'6" diver rod with a moderate action 10' rod, they will both be bending about the same distance up the rod when loaded and the 10' rod will not be reaching out any further than the shorter rod. Alternately, you can run the same length (and action) diver rods if you stagger the tip height of the rods. Most quality diver rod holders today have 15 degree vertical adjustments. Setting the outside diver parallel to the water and the inside diver one setting below this can negate the need for different length rods. If you find running a diver in this manner unsettling, then by all means go the different length route. Just keep you diver rods as short as possible to minimize the lever effect the rod places on the angler. Unless you have really long outdown rigger booms, many people can actually use a 7' fast action diver rod on the inside, and an 8' fast action diver rod on the outside (or 8'/9' with extra long outdown booms) and have a much more enjoyable fishing experience than using the moderate action 10'-10'6" rods on the market today. Finally, consider running the new 19 strand wire on your inside divers. It is much more forgiving to rod guides than the old style 7 strand wire.