Interestingly, we've been seeing a few more DPs of 20k matches (e.g., 50k -> 70k).
My initial thought process for trying the 65k -> 80k was because I thought 15k was the most CSRs will match, but it's looking more and more like it may be 20k. It may be worth trying a 65k -> 85k match, but I don't have any new 65k's to try at this point.
I will definitely be trying a 50k -> 70k when I open a new card in a few weeks, however.