In theory, being at altitude makes you easier to spot, and although diving down to the target gives you a greater entry and exit speed, I suspect the 109 or 190 will still overhaul an IL2 pretty quickly.
That really leaves being low down, and from what I've read, for an aircraft to blend in, it's got to be really low. Regardless of what you choose though, multiple aircraft have a better chance of getting through, provided a reasonably tight formation can be maintained, and you might want to consider shortening the icons further for enemy aircraft. Ground pounders need to be able to slip in and out of the target areas without being detected to have a good chance of survival.
How about changing routes to and from the target, so you approach from an angle the dastardly Arthur does not expect? Ignore the waypoints and sneak around the back as it were.
The last statement would have been funnier if Snacko hadn't beaten me to the punch.
Jabo