mfuller

Good information here.
I agree that hollow anti-roll bars are preferable for the weight savings (less unsrung weight is always a good thing).
Mark already pointed out why a hoolow bar won't work in back. The front bar has issues with space constraints. Even a 1.125" (28.6mm) bar is very tight - where the bar is bolted onto the front subframe with the midpoint brackets, it is in very close proximity to both the front edge of the unibody and he steering rack. You might be able to go a smidge larger (early on, Mantapart suppsedly made a 30mm bar that fit in there), but I'm not certain what engineering challenges that would entail.