OK, pootled around for a couple of hours, stopping to adjust the cable a tiny bit from one side of the marks to the other. The best I seem to be able to get is the 3rd gear slips unexpectedly. It is like the gear cable is suddenly too long. It seems like if I start to shift to 4th but hold it half way, the gear seems to work. If there was an adjustment for every gear in the twist knob, I could fix it.
How about the X-RF8'w' hub? Now that a few people have had a chance to try it, is it worth the time, effort and money to change to that hub?