That's what I thought Pumblechook, sounds like I'd have to have knowledge of, and access to, the circuit in order to lock phase.
What made me even think about it is Honda offers a feature on their EU series generators that allow two of them to be connected together with a special cable to...
I was wondering if it's possible to use two or more-off-the shelf DC-AC inverters in parallel in order to provide more AC power?
It occurred to me that unless they were in phase, problems could result.