900 elo can solve this in 30 minutes
FYI there is a version of Stockfish which is strong at solving tricky mate puzzles:
http://github.com/jhellis3/Stockfish/tree/mate_finderYes, it's strongly recommended to use Stockfish Matefinder to analyze human games. The regular Stockfish is only optimize to play against computers. It has weakness with zugzwang positions and to announce accurate mates.
