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I found this article which shows that there's a MK2 pcb which has this done and also has the ground tracks removed by the connectors to avoid shorting the centre pins. Are these the ones that the BATC shop is stocking now?
As there's no ground pin on the module, I assume that the pcb must be connected to the heatsink to connect the grounds together. Is there anything to be gained by making a direct connection from the module tabs to the nearest point of the pcb groundplane?