I've mounted my display and it seems to be sagging forward. Is this normal?

Yes, the nature of steel is to flex and rebound allowing it to absorb shock more effectively and protecting the display in the event it gets bumped. That same quality will mean that larger and heavier displays will have a tendency to sag downward especially with mounts with more complicated mechanism like those found on our tilting/swiveling designs. The forward tilt can be easily compensated for by tilting the display upward and locking it in a position that hold the screen level.