Never worry about low-end when porting, unless you want to ride with a stock clutch.New top-end power is always taken out of the low-end power.
The portmap that Eric posted is very conservative compared to my portmap. Elliot's portmap looks a lot like mine, altho I didn't raise the intake like he did, I just widened it and shortened the piston.
My TCCD gets a good 45MPH, but that's because I gear low. I'm not a top-speed guy, I am however a high-rev cylinder guy. My kit screams (11.5k RPM) and absolutely rips with both a Proma Circuit and a Proma LowBoy (More top-end revs than the circuit).
And as a final tip: Always bring the exhaustport to 67% of the true bore, as it will give you maximum torque with minimum piston(ring)wear.