Well I have perused and read some quick texts by historians and I can't find any evidence that the hoplon and pelta were "interchangeable"
The hoplon had a very unusual system for holding it which forced half of it to tick out to the left of the wearer. The pelta and other shields of the period has "center grips"
The big difference is that the hoplon basically leaves you exposed, meaning you are relying on your neighbour for protection, thereby encouraging the phalanx to stay cohesive and tight. The biggest weakness of the spear formationa t the time was that it would break apart. The introduction of the hoplon meant that this rarely happened since the Hoplon was pretty bad at offering protection when out of formation.
The "crecent" style pelta was used more like a buckler and was carried by light trrops and mounted troops and provided both light spear and javelin support. In fact the Holon and metal reinforcement while the pelta was usually hide and wood.
It has been a long long time since I did classical studies so I had to go refresh my memories.
The hoplon had a very unusual system for holding it which forced half of it to tick out to the left of the wearer. The pelta and other shields of the period has "center grips"
The big difference is that the hoplon basically leaves you exposed, meaning you are relying on your neighbour for protection, thereby encouraging the phalanx to stay cohesive and tight. The biggest weakness of the spear formationa t the time was that it would break apart. The introduction of the hoplon meant that this rarely happened since the Hoplon was pretty bad at offering protection when out of formation.
The "crecent" style pelta was used more like a buckler and was carried by light trrops and mounted troops and provided both light spear and javelin support. In fact the Holon and metal reinforcement while the pelta was usually hide and wood.
It has been a long long time since I did classical studies so I had to go refresh my memories.