How many smash burgers can you cook on your XL?

I just made smash burgers and the grill was not hot enough (fully preheated to high and then some) to get a good sear. I am thinking it is because I cooked six 4oz burgers at once. I know… larger than optimal for smash burgers but I could get away with it on my Blackstone. I’m thinking the cold meat cooled down the grill too much. It is either that or the grill is underpowered for some reason.