good painting, especially the leather parts, this figure is very beautiful , it's a pity it is not correct for historical reproduction , the helmet is for a centurion or decurion not for an ufficial... but never mind ...however is a great piece and i thing very enjoing to paint.
I don't think there is anything wrong with the helmet, per se. However, if he's supposed to be a centurion, then the crest should be transverse (side to side), not fore-and-aft as here.
However, I doubt that the cuirass would have been made of iron. The Romans seem to have been incapable of working iron sheets that large.