I would say yes, as long as it is comfortable, even try a combination of adjustments. lower the Ab/cod, take a photo and see how it looks.
Lower the chest plate slightly, again take a photo and see how it looks. Work out which feels the best, vs looks the best.
Don't be too concerned about your helmet not resting on your chest plate, everyone is different shape and size so it's not going to be a decider in any approval.