Is it possible to use an h-shifter through all 12 gears on the Gavril T-Series?

The first 6 (7 really, since 7 gears can be bound) gears I can shift using my G27's h-shifter, but after that I have to use the flappy paddles. I was wondering if maybe I missed a "range" button bind to let me get through the next set of gears. A low/high auxillary transmission would be perfect for this, since we can do similar stuff to the D-Series and it's low/high range boxes.

For reference, I play a good bit of American Truck Simulator, and it's really enjoyable being able to go through the first 4 or so gears then flip the range button on the SKRS shifter to go into the high range of the transmission. So, I guess I'm basically looking for something similar to that.