That's some really crappy air... If it were 50 deg out and DA was 200, you should be a couple tenths better. Fall, cool dry air is great for ET. All of my Flex 12 sec times were with 600 DA. First in IA at a track that is 850 ALT when 45 deg, and the others using DR's in Bradenton, FL Alt 30 ft. 75 deg. So those runs with the same 600 DA were much better, though fractionally slower.
If you're going for best ET, you want to stage as far back in the box. To do this creep forward and set first light, then creep really slow till second light comes on and stop.
If you're trying to beat a similar vehicle, you want to get as far forward in the box. Believe the box is about 11" so it isn't much from front to back, but a fraction is just that when posting numbers or winning.
It's addictive!!!!!!!!!!!!!!! Darreli and 4DRHTRD are 2 of our resident experts... I'm just a novice compared to them.