I think it should support serial stack more than 2 Spark as it have 2 200G CX-7 ports, but how to assign work loading is a problem. NV may not provide official tools.
Besides, per your another topic, I’m agree that connect more than 2 Spark through Switch is also another solution, and I do really think if will have a 3rd party code to support task assign well, it have chance to use a cheaper lower speed Swith instead of expensive NV 200G port swith like QM8700, because we may not really need 200G speed data transfer. Do you know some other switch have less quantity 200G port(or 100G port but more cheaper and smaller?)