I'd play it safe and burn at the stated 2.4 speed. Also, shut down your antivirus and scan for spyware as these things can screw up a burn more so than the drive or discs themselves. Finally, regardless of burn-proof technology, don't use the computer during a burn. I found it can make the difference between a pixelated scene in a movie and a not pixelated scene.
Don't forget to update your firmware in Safe Mode.