I find myself tooling along quite often at 50 mph in 5th gear, and I have no misfire or drive-train lurching at that speed, as long as the primary chain is adjusted properly. I don't necessarily agree that 2000 rpm is "lugging" the engine. Now, if you are sitting at 2000 rpm and decide to nail the throttle, then yes, that is definitely not a good thing to do. But under light load, 2000 rpm in 5th is fine (and a lot quieter than using 3rd or 4th at 50 mph). Just remember to downshift if you want to accelerate. BTW, if you look at the recommended shift points that H-D has in the owners manual, I believe you will find that they recommend shifting to 5th at about 45 mph. IMHO, that is a little too low, and right at the rpm where the engine runs the leanest from the factory. Of course, that is the same recommendation they use for all their bikes, and isn't specific to the 103.
Jerry