I do not know about the H-Shifter..
The H-Shifter is not able to use in any game due the high gear you will get to.
But you can still use the gear stick, just change the stick mode
ow.. It would be pretty cool if the game had a HIGH/LOW button. Split gears
4L, 5L, 5H and all that...
BTW I noticed that most american truckers don't use their clutch when they shift