Where would the Centurion stand in a battle line?

[M. Caecilius]

This, however, may be just a piece of wishful thinking on his part. I'd be inclined to trust casualty figures over theoretical works here as something close to real hard data.

Good point, but do we have any casualty figures for the centurions or for their feats of daring for the Polybian and earlier periods?

There seem to be some heroes. Ennius is mentioned as a centurio by Silius Italicus, but the text is too Homeric to be taken at face-value (although probably based in fact). Spurius Ligustinus (in Livy) does 34 awards and 6 civic crowns but mentions only that this was uirtutis causa, which could mean anything from Polybius' leadership abilities to Caesarian daring.

Beyond that, there is no contradiction in being steady and sedate in spirit and standing in the first line: they'd merely be expected to motivate their men not to give way before the enemy, to advance steadily and keep ranks, rather than risk them unnecessarily in a headlong rush.