That's the one - well done! My own solution uses the last Stacker and Fencer slightly differently to release the bottom crowd (I stack slightly behind where the first stacker built the wall, with a slight gap in between them, and then use a fencer through both... if you make the second wall at the same time as the first wall, you even save an extra lemming), but your solution is an acceptable variant. Originally, a Stoner was used in that pit, but a Stacker is much more intuitive. Thanks so much for your testing and patience. Guess 13 was lucky for me!