I really am thrilled to have the extra 4" of Z travel. I can now use a 2.5" finishing mill on 3" high workpieces. Like this:
In the event you have disassembled the saddle lock from the leadscrew and it won't lock, remove leadscrew, and reinsert it into saddle lock with no gap between lock lever and other brass piece. Friction between brass pieces provides the lock.