I've cracked 3 rear hub/axles while endurance racing, and know of a few other Supra owners with the same problem. The failure point seems to be the e-brake access hole and then a crack radiates to the center of the hub.
I've spoken with 2 friends who are machinists and they both mentioned that the radius of certain areas is not up to the stresses of racing or high power levels. I asked about creating a solution and the best answer was billet Chromoly replicas with updated radiusing where necessary.
The first drawing is below and includes (4) and (5)-lug options. The machinist mentioned that the lug and e-brake access holes would be the last stage of production and could be different on each (I don't use an e-brake, and will be using 5-lug wheels on a new project).
At this time I have no idea on price, but the more sets that are made will result in lower price for all. The reality is that they will be expensive ($1200-1500 set?). A few people in my race thread have expressed interest and I wanted to capture a bigger audience here.