I have trouble seeing the plane when I shrink the map to make it where I can fly with it open. I find it very valuable to do so. You would be surprised how many times you save yourself from being blindsided with the map open. About a 2 inch square. Its easy to see that red dot coming for you. But what I have trouble with is as you fly around your plane moves around the map. It can get over the City or most often over the numbers designating the area of the map sector. Or it can just get over a dark colored portion of the map. I can still see the plane but not what direction its going in. So I can't tell if I'm flying at the Cons or away from them. Of course by the time you figure it out your surrounded by the MoFo's. I think I'm stating my problem with the plane a little more clearly this time. I apologize for not doing so in my first post about it.
KIMO 
Or, you know, you could check your six once in a while

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What I do is this: Leave map at full size, zoom in almost all the way, and close it. Every time I get a break, open the map up and scan it for incoming red blotches, which signal an STD... err, horde.
Now whoever told you to keep your map open is an idiot. Don't blindly follow advice because someone told you to do it. Try it, form your own opinion, do what works best for you. But even more importantly, don't reject other advice out of hand because it doesn't match up with the first thing you heard.