Thanks for the feedback, guys.
I went with Red 4 simply because of the colors. I have a thing for mustard yellow for some reason. I will do other schemes in the 1/72 scale kits I have to build (thinking Red 2 and Blue 1), but when I get around to building the studio scale resin X-Wing I have, I may very well do Red 4 again, but be sure to go darker on the yellow and weather her up a bit more.
The droid head is an R4. I got it from a long out of production resin droid set. Technically the head is supposed to be round at the shoulders and then go to a square at the top, but I didn't want to muck around shaping it and screw it up!