Looking super, my friend @lis! OD is great! No clue about the exhaust...

Always following your build with great interest, @lis! Don't worry about the exhausts differing a little from each other.

Exhaust stain do look very nice, Bernard @lis

@lis i fatal mistakes are the nature of our hobby, do not despair - you did not sign up for Lego, my friend! I would not worry about the size of the decals considering that in WWII there were so many different paint jobs on those planes anyway. If it does keep you awake at night (which it probably does after all the work you put into - i think most modellers are somewhat obsessive, haha, just speaking for myself) then you might consider covering it up with some of that neutral grey and then buy some additional decals on evilbay? I would not do it, enjoy your absolutely lovely B 25 and just build the RAF version next.

@fxrob On this picture You can see differences in diameter.

I have spare star kits just in case as I've generally used an aftermarket kit from DK-Decals. Although even here I noticed that they differ slightly from each other in navy blue color compared to the Airfix markings. Hence all the confusion that each star had a different size. It seems to me that Airfix took the dimensions of the national and military markings from the B-25 aircraft that is parked in front of The National Naval Aviation Museum. And in my opinion the US Army marking was too small. So I used DK-Decals right away. Then I started to choose the stars, I chose the right one in my opinion and then I glued the wrong one. Sometimes I feel handicapped. The question is whether sticking a star on top of the star will cause the one underneath to show through and look bad?
PS. I tried to break these stars off with the methods from the Internet, but they stuck so tightly that it didn't work. I will add that the same size is on the top and bottom surfaces. Only the diameter does not match.
PS2. I try to buy B-25 in RAF version, but this kit is hard to buy 🙂

@fiveten Thank You. So You will leave it as it looks?

1 attached image. Click to enlarge.

@johnb No matter what, the decals actually worked out really well. I used Tamiya decal liquid this time with very good results. Will sleep on it until tomorrow.
To improve and change the mood. Ruptured Duck.

1 attached image. Click to enlarge.

@stephen-w-towle
The same size of the decal is on the top and bottom of the wing. Even the decal underneath seems bigger but it's a visual illusion. They are the same (a bit too small). I'll leave it until tomorrow and evaluate what I want to do with it.
PS. I tried remove decal with tape and as never the decal didn't even move 😀

Found another photo of a Doolittle bomber being launched. Open the photo its a good clear photo with sharp image of the decal in question. There are always more questions than answers with these things and the distortion of the images given the camera angles and who ever was involved in painting on the stars. Both photos show the star touching the aileron on the trailing edge while the leading edge is set farther from the leading edge of the wing.

1 attached image. Click to enlarge.