That middle bolt location is right next to where xdrian's case cracked. I got my spare case open and sure enough the support is very sparse there. While the bottom side of the case housing is a fairly beefy curve, the top is flat and not very well supported, so this brace will tie that area into the much stronger front bulkhead and bell-housing/engine block bolt locations.
Basically, the ring gear & diff carrier are being shoved into the driver's side of the case by the pinion gear... This should help to resist flex in that area. I'm not too concerned about the passenger's side of the diff housing as it's not seeing nearly as much force applied by the ring & pinion. This would probably be well complimented by the main reinforcement, as that will tie into the other side of that rear 10mm bolt.
It will be going on xdrian's new case. He's saying that he's putting down a 10.8 @ 128, and with the busted case, I'd believe it. While it has yet to be tested, I'm pretty confident that it will help out. When a case actually cracks, it seemed to me like a logical step to add a steel reinforcement at the section of webbing that failed. But I guess we'll see how it holds up