Thank you for clearing that up, I wouldn't have thought we'd use club arena's for U21 scrimmages. I couldn't find it anywhere in the rules or forums, and I thought team ID meant U21 team. Maybe it would be good to change the error message to a more clear one, or put it in the rules, or the NT forums.
Is there any effect to the home or away selection, since you give a club ID that seems like a neutral site?