Here's a link to a 911 with PDK and manual. I use the same technique but limit my RPM to around 3K. Too low and you'll have to take it easy on the clutch. 3.5K will be more forgiving if don't let off your clutch easy. Do this right and both you and your car will smile
http://www.caranddriver.com/features/09q3/how_to_launch_a_2009_porsche_911_carrera_s_manual_ and_pdk-feature