haven't tried overhead with my flux yet. i'll have to give it a whirl soon 
For overhead, set the machine similar to what you might do for flat, maybe turn the wire speed down a hair.
who in their right mind runs a structural vertical weld downhill??? 
There are certain codes that require downhill welding. Mostly all plate is welded uphill, but there is some codes that call for downhill MIG, especially for root passes, on pipe. Also, the API 1104 pipe welding code requires E6010 root and filler, all downhill. Conversely, the ASME Section IX code for pipe welding requires all uphill.
