There is not a question of strength here, I already have tested the product, it works well. As far as the tooth engagement is concerned, there is a total of 8 teeth meshing together, 4 teeth per gear block, one gear block per side of diff. In a traditional carrier there are only 4 teeth contacting at any moment. Lincoln locking has been used for years, which is strong except the gears are so dang hard, the weld does not stick very well potentially falling out and wrecking literally everything in the differential. So, 8 teeth should do the job just fine. I have done some calculations to even back up the aluminum strength issue, it is just easier to manufacture the product using steel from a marketing stand point. This way no convincing is necessary, its just easier. The calculating that I did do is based on a 4140 axle shaft having a 1in diameter (which I am considering the weak link in a dana 44. This axle shaft shears around 1200ftlb. If you consider the cross sectional area of a gear block tooth and multiply that by 8 for the number of gear teeth in the mesh, the shear torque is ruffly 8800 ftlb. Having said that, the bolts only hold the blocks together, they are not subject to torsional forces. Because the gear blocks are designed to wedge into the spider gear arrangement at a 80 deg angle 90% of all rotational forces will strictly be in a rotational fashion, not in an outward fashion pushing the gear blocks out of the arrangement. The 4 bolts can handle about 55,000 lb in tensile load which is not an issue to take care of that 10% of the rotational 1200ftlb.
ps It is actually not possible to contact 2 or more full teeth on each spider gear because you would not be able to install them. (look straight down on the spider gear arrangement.)