I am not sure that this is correct. Can one group be reused in multiple group configurations? How does the system determine which grading configuration to use when assigning students to that group? Say you have 50% of your students in group "1" (because the group configuration used to assign students to group "1" has two groups in it), then you set up a different group configuration with 5 groups in it, including "1" which already has 50% of your students in it and 2, 3, 4, and 5 that only get 10% of your students each. Wouldn't it skew the experiment if the sample sizes are unequal? 
(This is what I *thought* this was going to be about...
For each of the group configurations that you define, students are assigned to one of the possible groups. Students remain in those assigned groups regardless of how many content experiments you set up to use the same group configuration...)