I don't know if documentation exists that says it is or is not supported. I was actually hoping that someone from Symantec would've responded by now...
My questions with such a setup would be:
Can you guarantee reliable cluster interconnects (heartbeats) ? Remember that the interconnects MUST be independent.
Can you guarantee reliable access from both nodes to the same shared storage?
If you can configure this in a lab environment and do failover tests as well as simulate all sorts of resource failures to test expected behaviour, I don't see a problem with such a configuration. A critical concern in the evaluation process would be to ensure that Single Point Of Failure (SPOF) is identified and eliminated. You can actually do that up front by drawing the configuration and pinpoint any possible SPOF.