When designing patches remember that AH patches are sewn, not printed, which gives certain restrictions to detailing but it also makes them quite unique.
Eg. the angle of the bomber in midi's design is good because the outlines are nearly horizontal and vertical giving a clear shape when sewn. It is possible however that the smaller bombers may have their engines sewn too close together making it look rather odd. If the plane will have more oblique angles it may have to be bigger to give it enough detail to be recognizable.
I think 3 is a good number of planes and maybe of slightly different sizes.
-C+
PS.Maybe one version with map outlines of Germany behind bombers? Only outlines because if it is filled with some colour the colour is also sewn on patch which somewhat reduces the accuracy of objects sewn on top of that surface. That would probably also translate to one guideline: If you are going to make small details on patch make them on base colour of the patch so any other sewing under the details will not distort them. Although I'm not sure if the makers are enthusiastic about making patterns on the base colour only...
Edt. One nice base for B-17, more oblique angles but he angle is nice:
http://sill-www.army.mil/Graphics/aircraft/b17.jpgFound this too, sry a bit OT:
http://mywebpages.comcast.net/mharneyma/image/b17sunf.jpg