Only insofar as it increases SA, but most of the complaints I've seen here refer to aim. If you were to disable guns in F3 mode, that would have no effect on the SA component.
Yes, aim as in using it to line up your plane for the shot when otherwise you could not see the bad guy. Also for aiming at GVs. A lot easier than using the the inside. You can use your tail as your aiming point.
Most of the complaints about the use of F3 mode in the MA center on less than godly planes like the Sturmovik, but I don't buy that F3 mode turns Sturmies into unkillable snapshot machines. I suspect that guys like ghi would probably still continue to be successful in them with or without F3. His SA might take a hit, but he's obviously quite good at suckering people into making bad passes.
Not unkillable. In those situations they use it to take down one or two guys no matter what the cost. However, being able to see people other wise not visible does help. As I said, I use a P40 sometimes. Not a great plane either. Can I get F3 also?
But, I don;t care about the MA (unless of coarse someone asks). There is no reason to have it on in the DA lake or other fields.
