I am going to pull a Derek and quote my self for the sake of the fact that I realized that there is important info I was missing.Also, the other thing I wanted to point out is that it is important to meter the system anyway. The OP never mentioned what kind of 3 phases service is in the building. If they have a ∆ (delta) tap transformer they could run into issues making the adapters they want if one of the hot legs in the connector is the wild leg. In a Y tap situation they would be OK (in theory) but then it isn't a 240v system, and I think that is important to point out. Hot to neutral in 3-phase Y is 110v, phase to phase would be 208v.
The OP claims he is working with a 110v/240v system which to me suggests that it is a ∆ tap transformer (or he is misinformed by the venue or his electrical theory). This seems like an area for concern, and some metering. Why? Most dimmers and ML distros and the like that I have worked with are designed for 3-phase Y NOT ∆, they want every hot-to-neutral connection to be 110v.
I guess the point is that the OP and us NNED MORE INFO! Make some phone calls, and figure out what you are really working with!