I made a script for this a few years back. Assuming it still works correctly, there are 33 users with 0 (net) inclusions on DT2, and 308 with 1 inclusion:
0: 33
1: 308
2: 94
3: 61
4: 34
5: 23
6: 15
7: 9
8: 7
9: 9
10: 10
11: 7
12: 4
I'd say the minimum should be DT2 strength (2). That moves about half the users, and makes it less of a "burden" to include someone.