Thank you, Magnus. You're right, t1flg, t2flg etc field names in each doc are incorrect and was a typo as I was mocking up the documents. I would instead need only a generic field for flag tflg and another for data as tdata with an indicator tind to represent what the fields represent (t1, t2 or t3).
You've shown me the direction. I will follow on this and revert if I need any additional help.
thank you!