Track usually uses Core 2 (the Crunch Time/Solution) core in their lighter weight balls. I don't know the RG and diffs in the lighter weights, but Track doesn't even publish the numbers for the normal weights either. Probably medium-ish RG (2.54 or so) and medium to medium-low diff, 0.035-0.040.
In their Core 2 balls like the Crunch Time and Solutions, I've seen a reference to a "Rocket" core being used in lighter weights, but I don't know what it looks like.
SH