Hmm...let's see.
Guy's head is just a bit shy of the top of the valve train...
On the other hand:
Guy's head is just a little shy of the top of the valve train...
Looks about right to me.
Also, it's true that overall the diesels seem a little small, but there are a lot of pipes and valves overhead that don't seem to be in the game. That can change a lot, as well as the afore-mentioned camera angles.
Looks real good to me.