[RC-Monster Mike]

7075 is about 1/3 stronger and 1/3 heavier than the 6061 aluminum. This strength difference is not noticed in the diff cup application, as the 6061 is plenty strong for the job(so, you wouldn't notice the difference with either cup-performance would be the same). New spider gears in a new diff cup requires very little shimming. As serum said, you want the mesh as tight as possible woithout any binding. When built properly, they can take quite a bit of punishment. The 1/8 diffs are an upgrade, as they can be tuned with diff oil and have more spider gears inside(so each each individual gear has less demand), with a price upgrade as well. I use both(different trucks) with no problems. I like the tunability of the 1/8 diffs, but the FLM cups inside aluminum cases work excellent on the track (I like lightweight oil for the track I typically run on, due to the rough terrain-more diff action = easier to keep straight).