Mark,

I totally agree. I thought that the weak point of simple mounting block are exactly what you mention. The movement of wood (in the mounting block) under lateral load from screw or the screw itself bending. I thought use of hardwood mounting block, a super tight fit and screws appropriate in shank size would overcome that. Never disagreed that french cleat is not superior.

I would be interested in knowing if Joe Jensen figured out the reason of the sag and whether it could be remedied. His decision to go with french cleat may be because he did not think so but still bd good to know.

Imran