Rear Diff. Fluid - Redline ShockProof Light or Heavyweight?

[Ice Racer]

Ok, so I've researched what kind of fluid to use to a certain point. I've narrowed it down to Redline ShockProof. But there are two kinds: Lightweight and Heavyweight. Here's my dilemma. I'll be racing my car on ice in the winter. Engine warmup time is ok, but the short drive from the paddock to the grid is not sufficient to warm up the drivetrain. So on one hand the lightweight would be a good choice because it works better in the colder climates. However, after a lap or two it will get hot and I may need the properties of the heavyweight. Not sure. Can anyone suggest one or the other?

 

[2point3Tsi]

My car loves that stuff, heavyweight in the dif and xfer with lightweight in the trans. slightly stiff for the first few minutes then it shifts like butter, feels like the gears just fall into place. This is on my DD so I can't see it taking more than a few shifts/minutes for the fluid to warm up and move around(even though the heavyweight looks like molasses )