I have always useed group learning for hands on activities. Large scale construction projects need a crew to do the job and my focus is to make sure that everyone in my class becomes a foreperson, at least once. Once the forepeople are picked, they are able to pick the crew. However, as the instructor, I have veto power over any pick to prevent crews being populated by the same people over and over again. One other way to get diversity in each group is to have the forepeople pick one person at a time, Typically, with a few rules set before the crews are pickedd, the crews formed are balanced and have a new combination of people.