My buddy here was moving away, and wanted a combat shirt - Badly. Our local surplus store didn't have any good deals on a legitimate issue shirt, so she picked up a $3 ACU undershirt, and I cut up an old ACU blouse. A little while later, we have a passable UCP combat shirt.
On the technical side, the undershirt was size "Extra small", and the blouse was Medium Regular. If anyone wants to imitate this kitbashing, it would behoove you to get similarly sized clothes so that the sleeves will match up more closely.
The inverse of this shirt was also created - ACU vest, with tiny t-shirt sleeves. Pictures will go up as they become available.