Yep, Aaron emailed me the corrected part within a few hours of my telling him about it; thanks for the fast work, Aaron! Here's my subsequent progress (with the fixed part):
The cannon was kind of finicky at this size, and the center internal wing section (is there a better term for that?) was surprisingly hard to get in there correctly. Maybe there was a better order I could have done things in to make it easier. Fortunately, a lot of the mess will be covered by the engines on both sides of the fuselage.
Moving on, I noticed what looks like another coloring issue: the thin white band on this part (it's a fuselage section toward the rear) is supposed to be red, according to the photos I've seen.
I used a red marker to color it myself on my already-printed part, but Aaron might want to change it in the files as well.