Arm template copy variable

Hi All, 

I'm attempting to use the copy function within variables section of an ARM template. I'm trying to dynamically assign x number of NICs on VirtualMachineProfile inside the NetworkProfile. This is to enable open networking mode: https://docs.microsoft.com/en-us/azure/service-fabric/service-fabric-networking-modes.

This is my variable:

"Copy":[{"name": "networkInterfaceConfigurations","count": "[parameters('SFAdditionalNICs')]","input": {"name": "[concat(variables('sfNodeNicName'), '-', copyIndex('networkInterfaceConfigurations'))]","properties": {"ipConfigurations": [
                            {"name": "[concat(variables('sfNodeNicName'), '-', copyIndex('networkInterfaceConfigurations'))]","properties": {"primary": "[if(greater(copyIndex('networkInterfaceConfigurations'), 0), 'false', 'true')]","loadBalancerBackendAddressPools": [{"id": "[variables('lbPoolID0')]"}],"loadBalancerInboundNatPools": [{"id": "[variables('lbNatPoolID0')]"}],"subnet": {"id": "[variables('subnet0Ref')]"}
                                    }
                                }
                            ]
                        }
                    }
                }
            ]  

and this is how I've applied it:

"networkProfile": {"networkInterfaceConfigurations": "[variables('networkInterfaceConfigurations')]"
                        },

I'm getting the following error which suggests the variable is not being recognized:

VM scale set NetworkProfile must have exactly one NetworkInterfaceConfiguration with primary property set to true. VM scale set NetworkProfile /subscriptions/124e0329-b994-45b6-9ad5-a8c7ca40f282/resourceGroups/ATLASDEV21-RG/providers/Microsoft.Compute/virtualMachineScaleSets/atldev21isf-vmss/updateGroups/ee26fc51-2bac-4018-920c-7c69490e6457 has 0 primary NetworkInterfaceConfigurations."

I've referenced the following examples

https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-group-create-multiple

https://github.com/Azure/azure-docs-json-samples/blob/master/azure-resource-manager/multipleinstance/multiplesecurityrules.json

https://azurecitadel.com/automation/arm/lab5/

https://stackoverflow.com/questions/49629408/azure-arm-template-copy-array-to-object-array