So in theory I need to turn Idle richer until it doesn't die when vertical? Another symptom is that when I back down the throttle to idle (not including the trim to kill it) it gradually slows down over 15 or 20 seconds. Still a fairly rough idle. Could it be it's still too lean? As I turn the screw I noticed it turns very easily almost as if vibration might have got it out of whack in the first place.

I suppose the next step might be to RTFM that came with it to set everything back to factory reccommended.