Obviously the boat's length make a difference in the type of carrier you can use. We use touring boats, one is 14' and the other 16', so a roof only system would not work for us. We also have an 8' truck bed, so the fiver will not hit the boats if they protrude out the back of the truck cab.
We have used the rig in the picture from the previous post for several years now and I would estimate we have put well over 20,000 miles on it with out any problems.
One thing I discovered after I started carrying the boats is that a substantial part of the strength comes from the boats themselves. In essence the boats tie the two racks together and act as truss member to keep the system from moving around.
