Have the recommender fill the matrix. The matrix compares you to your peers (or whoever your recommender decides to compare you to) by trait and thus provides additional data to your letter.
Additionally, you want to make sure that your letter reco answers all the questions that each school asks. Different schools ask different questions so if your recommender want to write only one letter then group the questions for every schools that you are applying for your recommender and have him/her address all of them by group. Some questions are repeats of course, but some are different. Schools would hate to get a reco letter that does not address all their questions, or even worse was obviously written for another school.
I would include paper reco along with your letter as well. You can fill in your paper reco and refer to your letter in the questions section and give it to your recommender. Note that some schools such as HBS do not allow paper reco. I think HBS is the only school but there might be others.