Crap, you're right. I forgot the 16.8/EMBE brought about the big crossbar diffs.

On 4S, that's really, really mild. The 4907 Diffs are still pretty tough, and should hold up fine against 4S.

Though, my EMBE (3908 Diffs) runs 5S, and changing over the rear diff case to aluminum has bombproofed it. 6 months and counting. Regular plastic diff cup, too.