Remember the Mini came in 12° 14° and 16° models and had a 43.5″ shaft. If you want something like that a custom-fitted M4 fairway might be about right except it will probably offer even more ballspeed and forgiveness.
None of the above matters if you can’t aim your putter correctly Experiment with offset and straight-in hosels — you’ll definitely aim one type better than the other. Then check the alignment marks. Do you prefer lines that run parallel to the target? How many lines? These are important questions that can best be answered through a proper fitting.
A “stability frame” design strengthens the toe and topline while optimizing perimeter weighting for improved performance on mis-hits while a more neutral CG location that’s closer to the center of the face improves performance on center strikes.