Your project sounds really interesting and I wish you well with it...close exploration of the processes and dynamics within the supervisory relationship is really valuable and much needed. While it does not attend to diversity issues, you may be interested in a reflective article I wrote in relation to the supervisory relationship, which does address some key dynamics (it can also be viewed on my home page on RG):
McMahon, A. (2014). Four guiding principles for the supervisory relationship. Reflective Practice: International and Multidisciplinary Perspectives, 15(3), 333-346.
Aisling, thank you for the reference and our project is considering diversity and difference as configurations... I would welcome your reflections on dynamics