On mine, I replaced the small hex screws on the rack ears with slightly longer ones, which seems to get an extra thread through the hole and helps a little. You can't go too much longer before hitting what is mounted on the shelf, but a little longer helps.
I also used longer screws into the bottom of the Television Studio HD. The ones provided with the rack shelf work ok for the Teranex Mini units, but the screw holes on the bottom of the Television Studio HD seem recessed a bit more and only get a couple of threads in with the standard screws (which isn't really sufficient).
For even more support of the rack shelf, I also typically install an additional set of rack extension ears going backwards from the rack shelf that attach to the rear rails of the rack. I use something like these rear support brackets (they come in different lengths depending on the depth of the rack):
http://www.audiopile.net/ERDI use a few of the vent holes in the side of the Teranex rack shelf and drill matching holes in the rear brackets. #6 screws (or probably M3 in metric) seem to fit through the vent holes pretty well.
When attached to the rack rails in both the front and the back, the rack shelf is much more stable. I have shipped racks with the shelves mounted this way several times without any problems.