Years ago I went 19T and never went back. Taller gears, no problem two up, and no reaching for 6th gear. You will be around 90 MPH, 140 KPH when 4th is winding out.
The biggest mistake folks make with 19T is starting at lower speeds to crank them up in 5th, you run out of HP. If you learn the depth of the gears you develop the HP with the RPMs and you will run over 100 MPH easily. 160KPH I think.
You will not have enough HP to reach your rev limiter in the taller 4th and 5th gears but at the attained speeds you won't need to reach way up there. 6500 seems to be the high end sweet spot for shifting when you push it hard.
