I started playing with another 1/48 Spitfire kit this weekend (can't resist them!) and wanted to try an idea I had about the kit exhausts. They come in the kit poorly shaped, with hemispherically(sp) shaped outlets and no flare. I wanted to get a set of those beautifully cast Ultracast sets, but everyone is out of stock right now. So, I took a .25mm round dental bur (yep, a VERY small one, roughly 1/2 the size of a #80 drill bit!) and ground out the outlets to more closely resemble the real thing. Then, to replicate the tiny curved slit, I lightly ran the little bur into the plastic to simulate the new outlet. Man, that was very tricky! But, I am pleased with them and think they look much better than they do as supplied in the kit.
Here the end is done compared to the two top ones that need to be finished yet:
Here is the completed one on the left with the part as supplied in the kit on the right:
Not exactly scale, but much better IMHO. Here's one on a real bird:
(Photo courtesy of PrimePortal)