If this is the one http://www.tegiwaimports.com/select-...tegra-dc2.html you're referring to then my observation is this. I do not trust any brace that has an elongated (oval) attachment bolt hole. My other observation of this brace is that it is going to sit very low beneath your car.

This one http://www.tegiwaimports.com/select-...tegra-dc2.html from Skunk2 on the other hand is engineered to fit exactly into the existing rear subframe and appears to include new pivot bolts that will pass through both the brace and the pivots (i.e they are lengthened) thereby tie-ing everything together securely. The body parts themselves, from a purely design standpoint are well shaped and braced for general use, bu if you've ever been tempted to jack up the car by positioning a jack under the middle box section, you'll realise how puny and weak that bit is. That brace will relieve that body section from the bending/collapsing load placed on it by extreme cornering forces. What those square pieces are for, I don't know.