I have been working with 2 faculty members on the same project. I took a class from each of them, and the three of us meet in person on a weekly basis. I think it's reasonable to assume that they've seen the same level of research ability from me.
I am planning on applying to graduate school, so I was wondering if it's appropriate to ask them for a joint letter? My motivation behind this is
- the two of them mentor me on the same project, so 2 separate letters may have unnecessary overlap?
- applications typically require 3 letters (I already have 2). For schools which you can submit > 3 letters, I would think they still value quality > quantity
- may be slightly less work for both of them (?)
I don't want to come off rude by asking the two of them to co-write a letter of recommendation for me. Is it generally deemed appropriate to ask two faculty members to do this? I think this is quite uncommon because on applications I only get to designate one writer per letter of recommendation (i.e. provide just one name, his/her title, email, phone, etc). If so, how should I phrase the question of asking both of them to co-write a strong letter of rec for me?