The most obvious change was his introduction of design and illustration to the monthly paper.
Animators like to think that UPA represented cutting edge art and graphics from the era, even the most avant garde of their productions (whether James Thurber, Saul Steinberg, or John Hubley's designs) were still a decade or so behind the young design lions of the day. UPA was exploring ground tilled by Ben Shahn and Works Progress Artists years prior.
Until about 10 years ago, print has always predicted trends in motion pictures. This newsletter cover from January 1964 anticipates where commercial animation was heading.