Sous Vide Beef for 24hrs @ 56c

I discovered Douglas E. Baldwin today. I also found this pdf, which is useful. I'll buy the book eventually of course, I love cookbooks!
I set out with the idea that I'd cook a small joint of Topside beef for later consumption, maybe as a lunch item. I ended up cooking it for 12hrs, which is obviously too long! I think maybe 6hrs would be plenty, you'd probably get away with 4. 
Mr Baldwin has a handy chart for cooking roast beef. He suggests that the cut should not be thicker than 7cm, so if you have a large joint, carve it up and bag it. Then cook it for 24hrs @ 55c. I have to disagree with the esteemed scientist. I found that the Topside cut of beef is quite lean, and therefore, as with the Rabbit saddle in the previous post, became quite grainy after a 24hr stint in the bath. It was still moist and tasty, but had that dusty grain of slightly over done sous vide meat.