Form covariance for an equation means simply that all the L 's can be canceled out. As I have stated before, Dirac may well need to be extended to quaternion coefficients outside , and this will enlarge the spacetime and the covariance group. Everything will be more constrained yet larger and more subtle just as we have seen happen here, when we generalize from the E algebra to the full D algebra. There have been arguments against an odd number of dimensions for nature, but Dirac algebra shows us otherwise. If not, then we should expect 15-spacetime, and the quark world is horribly complicated.
Many mysteries obviously remain to challenge the next generation.
Many thanks to the loyal few that continued to encourage this extended and frustrating effort. The relationship between the algebras E and D, for our future physics, is also frustrating. 2227 words - in WP5.1. To be posted on the MSU Physics Department Web Page.