If you're going to screw the bottom edge, doesn't that defeat the
French cleat method. Why not just screw it top & bottom and be done
with it?
The screws along the bottom are just to keep the lower edge of the cabinets
snug against the wall once they're in place.

Not that there's anything wrong with your method, but
If you can measure accurately, you can
accomplish the same thing by using two cleats. Of course,
then in the next earthquake, the whole thing will bounce off
the wall and kill you.