Thank you both..
I gave up on the LAGs, will keep things simple for now. It's not supported as per the following VMWare FAQ for v1 of the VSA:
A. Yes, from the vSphere Client on each host.
The VSA installer does not utilize more than 4 NIC ports configured as active/standby uplinks across the two VSA virtual switches. However, the administrator can manually configure additional active uplinks for either of the vSwitches or their component port groups via vCenter Server.
Note: This can be used to add redundancy, but not to increase network bandwidth between any two ESXi hosts. None of the vSphere NIC teaming load-sharing policies load balance/share network IO across multiple active teamed uplinks for the same TCP connection. In a three-node VSA cluster, the IP Hash load-balancing policy can be used to distribute network traffic among multiple uplinks, such that each pair of ESXi hosts communicates over a different channel.
For more information, see VSA Cluster Network Architecture in the VSA documentation.