Question about the origin of the Greek hoplite shield

[MeinPanzer]

That is the first problem, if it has a boss it probably does not have a porpax and a double grip- the boss usually, though not always covers the fist. For example, early greek shields had many "bosses". In that specific image the main problem is that the shield longer from porpax to top than it is from porpax to bottom, this would be very hard to handle as it would want to fall forward or back. The second image is better, with the cut outs being more robust in construction. If I had to guess, I'd say this is artistic error and the shield depicted had a single central grip- just like the Hittite shields and the Greek Dipylon. Also note the double grip system is oriented the opposite was as a greek Boeotian.

Though the Achaemenid style in which they were carved may lack naturalism, the attention to detail on the Persepolis carvings is immaculate, and the sculptors were clearly intimately familiar not only with Persian equipment and costume, but that of foreigners too. As Stephen has noted, the bosses on these "cutout" shields match very closely an actual example from Persepolis as well as at least one other from Samos, leaving little reason to doubt the depiction of such shields in these reliefs. A double grip shield having a boss is only a problem if you assume that a boss cannot serve a purpose other than protecting a grip hand. It very well could have been used to protect the structural integrity of the shield at its weakest point, or simply to provide added protection for the forearm which was held closest to the shield. There is no reason to doubt the fact that such shields had double grips.