It takes longer and more ammo to bag an opponent because Wingstrut fixed to the DM to reflect something more akin to the history of actual engagements. Currently, the average kill per sortie in a poll at his forum reads 1-2 kills per sortie.
Regarding enemy AI. His recommended setting is setting difficulty at 110% enemy setting in the game difficulty settings. This is the setting he developed his patch, and provides an AI with above average gunnery skills. He also set the DM at the default bullet mass that can be adjusted using the CM preference scale. Any adjustments above the default setting result in quicker kills as the increased bullet mass produces more damage.
One benefit of the increased DM is also an encreased engagement time which results in increased fun imo. This is something on the order of what has been accomplished in IL2.
Regarding the setting in Fly Now, I usually set Elite in order to see what the best will do when I encounter them in a campaign.
BTW: I recommend posting your questions at the Link Hentzau provided as Wingstrut is always at his forum for answers.
http://forums.delphiforums.com/1918/start