Bro, its not like that in GS. Unlike the Deluxe and Piaggio, if you want performance from the 5th gear of GS, you need to shift all the gears in their Powerband. There is no such thing like powerband in a deluxe or piaggio.
If you are trying to get maximum performance from a deluxe or piaggio, you have to redline the RPM before every shift.
And, if you want to get maximum performance from a GS then you must shift all the gears in their Powerband. If you redline the 4th gear of GS to 12k RPM it does 105-110km and when you shift to the 5th gear the RPM decreases and the speed gets down to 95-100 (like many guys complain).
If you shift to the 5th gear between 8-9k RPM, then there are very much chances that it will perform max and do 115-120km/h.