1976 and 1978 World Champion Jim Bertz conducted a very insightful interview of Jack Leonard on behalf of AcrobaticSports.com and the USTTAA.  You can read the interview in the document attached below.  The document also features some great articles and pictures.

Jack Leonard was one of the greatest tumblers from the pre-World Championships era.  He was crowned U.S. Senior National Tumbling Champion in 1972.  He was also the recipient fo the 1973 Griswold-Nissen Trophy.  In college, Leonard led the Ohio State University gymnastics team to the Big Ten Champion title. 

After his retirement from competition, he was involved in coaching U.S. international gymnast Dominique Dawes.  He is now living in Hawaii where he owns the gym called Kauai Gymnastics Academy. 

Link to Jack Leonard's profile

Link to the Kauai Gymnastics Academy's website

Link to the USTTAA website