A 6th gear? What 2 overdrives now are not enough?
Unless Honda changes some of the other gear ratios which I don't believe need to be changed, nor that a 6th gear is needed, but if there were a 6th gear then the 4th (0.843 27/32)which is an overdrive and the 5th (0.843 27/32)which is an overdrive too would need to be changed. IMO.
Here are the five F6B gear ratios.
1st 2.375 (38/16) / 2nd 1.454 (32/22) / 3rd 1.068 (31/29) / 4th 0.843 (27/32) 5th 0.686 (24/35)