Hey MIDNIGHT, glad to see the site addition is still there even though you sold your scooter! If you were a betting man, you would win, they did pull the numbers in 4th gear but I'm not sure why that would make a difference....but then again I'm not very mechanically inclined?
I don't know all the details involved, but it has to do with the ratios in the transmission, the time factor involved in getting from the beginning RPM to the maximum RPM (longer time in 5th than 4th results in more stable A/F ratios). You can get even bigger numbers in 6th gear, but the speeds at the rear tire become kinda dangerous, so the "compromise" is to pull in the next to highest gear. The 4th gear run is probably why your TQ/HP lines are "wavy" as compared to a 5th gear pull, which would result in a more stable (less wavy) line.
As I said, there are others here who can probably calculate the difference (in %) between 4th and 5th. A round number I've read would be about 5%, so your TQ would be in the neighborhood of 110 ft lbs, which I would consider to be within the "normal" range considering the modifications you've done to the bike.
Hopefully, somebody like GRC (Jerry), Doc1, or some of the other tuners on here will pipe up (no pun intended) and do a better job of explaining this than I am capable of doing.
This is my opinion, but you mention wanting to be able to pass on a two lane road without downshifting...again, IMO, if my RPM was 2200 or higher, I would not hesitate to pass in 6th gear, as that is when the stock 255 cams start really starts coming in, up to about 4K RPM. I PERSONALLY think rolling on the throttle and putting a big load on the engine at anything below 2200 is not a good idea and borders on lugging the engine, which is a bad thing to do to a HD. Gradually increasing speed from 2000 RPM without putting undue stress on the engine because of loading is fine, but if I'm running 2K in 6th gear and want to do something in a hurry, I'm going to drop down a gear and make it happen faster. That's just how I ride though...others do differently. I just do not like to even come close to lugging my motor, so err on the side of higher RPMs, within reason, of course. Again, IMO, there is never a need to wind it up to 6K unless you are in a race. I have DONE it, but don't make a practice of it.