I have been asked by a top journal in my field (mathematics) to referee a paper. The paper is very strong, but I feel that it falls slightly short of making the cut for this (very prestigious) journal. In fact I believe I would recommend acceptance of the paper if it was submitted to virtually any less prestigious journal. How would I go about communicating this sentiment in the report?
For example, I have thought about explicitly recommending some journals for the author to submit to.