I'm Tom's field-tester for the E model racks. A couple of observations: with this, or any other rack, it's a very good idea to Loc-Tite all your fasteners and check them for tightness regularly. Tom uses hex-head bolts for connections. While arguably not as snazzy looking as Allens, they are much easier to get torqued properly, and far easier to find should you need a replacement.
The lower left side mounting tab used for the side racks is tapped for a 6mm bolt. This should be replaced with a 5/16" or 8mm bolt as Tom and I did on my E. It's a simple matter of enlarging the hole with a hand drill and nutting the bolt on the back side. This takes about five minutes to accomplish.
On some of the other designs, there is a considerable load on the seat mounting bolts, which aren't very stout. Tom's design shifts much of the force down to stronger and larger mounting bolts on the frame.