I am applying for a grant and am strengthen my proposal with letters of support. I will probably need help in a domain that I am not familiar with (i.e. Ophthalmology). A friend of mine is an independent ophthalmologist working with several health institutions. He offered to support me and write a letter of support to be submitted together with the proposal to show the funding organization that there is someone who will cover the lack of knowledge in that area.
Actually, I have never come across a letter of support written by an independent person. Would this letter look strange in my application even if it fulfils its main purposes (supporting the applicant with what he/she needs)?