Several more ways to drop weight off the TC4 are to use the TC3 aluminum center shaft/output cups and the composite dogbones. The stock TC4 center shaft is solid, so it's heavy, while the TC3 aluminum shaft is hollow and lighter. The TC4 aluminum dogbones are nice and beefy, but also heavy.
Of course, this all depends on what surface you are racing on. I'd say keep the stock TC4 stuff if you are using a one way or spool in the front. Those put a ton more stress on the drivetrain when you hit things, so you need the heavy, beefy components. But, if you run a diff in the front, you should be OK running the lighter TC3 parts.
That said, I'm still a fan of the IRS aluminum diffs over the stock plastic ones. For me, the plastic ones just break too easily.