Sule set his eventual personal best in Tallinn on 20 June 1938, throwing 75.935 m. At the time, that was enough to place him second on the all-time world list, behind only world record holder Järvinen; Yrjö Nikkanen pushed him down to third when he twice broke the world record later that year, but Sule stayed in the all-time top five until 1953. At the European Championships in September 1938 he threw 70.50 m and placed fourth behind Järvinen, Nikkanen and Várszegi, beating his Estonian teammate Friedrich Issak by one place.