As an old cubmaster, I told the boys it was their choice as to which shirt to wear (this was in compliance with scout policy). If that blue shirt fit, then wear it. If the scout was busting at the seams, then it might be time to invest in a new shirt, preferably khaki as that would set the stage for crossing over to the troop. Everyone knew who were the Webelos scouts by their neckerchiefs.
However, don't forget about which type of Webelos badge will be given to the scout when he reaches that rank. The older diamond shaped badge is meant for the blue shirt while the oval badge is f