Patti, I've looked at some data regarding "average" sized men during WWII. I think 5'7"- 5'8" is about average. This would yield a pilot of about 13.5-13.6 inches. Or you could make them 13.5 and be just fine.
Something to consider is that our planes typically have less room inside the cockpit for the pilot compared to the full sized planes. Our materials are often thicker etc taking up inside room.

So what I'm saying is that a shorter pilot would be a plus IMHO.