NIH F31 sponsor has not graduated students or post-docs
I think the NIH sums it up well in their FAQs

Q20: My sponsor has little or no experience training postdocs. How should s/he address that situation when s/he writes my training plan?
A: Your sponsor should consider asking a more experienced faculty colleague to serve as a co-sponsor. S/he should provide a detailed, well-thought-out training plan, in which the roles of sponsor and co-sponsor are clearly delineated. In addition, a sponsor who has not previously trained postdocs should describe any other training experience that might be relevant, e.g., supervision of graduate students or mentoring of a collaborator's postdocs.

The NIH policy also says:

Sponsor(s), Collaborator(s), and Consultant(s). Are the sponsor(s) research qualifications (including successful competition for research support) and track record of mentoring appropriate for the proposed fellowship?

While the exact &quot;penalty&quot; to your score is not stated, the fellowships are competitive enough that any hit will be enough to make you unsuccessful.