When you are working on your thesis paper, you can hire one or two paper helpers to smoothen your work. Though you are hiring two experts, you need to make sure that they do not collide with each other. Distribute the work between these two supervisors, and your job will be done amazingly. Though you cannot make both of them as your supervisors, you need to make one of them your official supervisor. The other one can be termed as your co-supervisor for the thesis paper. Talk to them about your decision in the first place. Do not create any confusion for them. One of them can handle the content part, and mostly, this person becomes your supervisor and paper helper. The second one can handle the methodology.