<FONT face="Comic Sans MS">The differance is that most of us don't have 3 feet, so while the line lock is engaged you can remove your right foot from the brake and use it for the gas, while your left foot is on the clutch.
That said, I just don't get it. This is a non-issue IF you know how to use a clutch, especially a car with as much low end torque as a Viper. I don't care how steep the hill, as long as you have a feel for the engagment height of the particular clutch, when the light turns green, just release to that point and get on the gas and release the rest of the way and go. Done properly, you don't roll back an inch nor do you over heat the clutch. The slippage time should be is no greater than when on a level surface. You're just a bit more aggressive on the gas when the hill is steeper.</FONT f>