Unable to reach terms with the New York Giants, Strong signed instead with the Staten Island Stapletons. He played for the Stapletons for four years from 1929 to 1932. While statistics are not available for the 1929 NFL season, Strong was regarded as one of the best backs in the NFL. He started all 10 games at halfback for the 1929 Stapletons. In his first NFL game, he threw a long forward pass to set up the Stapleton's first touchdown and scored all of the team's 12 points on two short touchdown runs. He also had a 70-yard run in a scoreless tie with the Orange Tornadoes on November 3, 1929. Two days later, Strong had a 50-yard touchdown run against the Providence Steam Roller. At the end of the 1929 season, Strong was selected by Collyer's Eye and the Green Bay Press-Gazette as a second-team All-Pro.  In 1930, Strong appeared in all 12 games for the Stapletons and scored 53 points on two rushing touchdowns, five receiving touchdowns, one field goal, and eight extra points. His point total ranked third in the NFL in 1930, trailing only Jack McBride (56 points) and Verne Lewellen (54 points). On September 28, 1930, he caught two touchdown passes, threw a 40-yard pass that set up a third touchdown, and kicked three extra points in a 21-0 victory over the Frankford Yellow Jackets. In December 1930, he led the Stapletons to a 16-7 victory over the New York Giants for the pro football championship of New York City; Strong accounted for all 16 Stapleton points, running 98 yards for a touchdown, passing for a second touchdown, and kicking a field goal and an extra point. He was selected as a first-team player on the 1930 All-Pro Team by Collyer's Eye and the Green Bay Press-Gazette.  In 1931, Strong appeared in all 11 games for the Stapletons and scored 53 points on six rushing touchdowns, one punt return for a touchdown, two field goals, and five extra points. His 53 points ranked fourth in the NFL, trailing only Johnny Blood (84 points), Ernie Nevers (66 points), and Dutch Clark (60 points). On November 22, 1931, Strong scored all 16 points in a 16-7 victory over Cleveland; he had two rushing touchdowns, including a 50-yard run and kicked a field goal and an extra point. At the end of the 1931 season, Strong was selected as an All-Pro for the second year in a row, receiving first-team honors from the United Press (UP) and Collyer's Eye.  Strong's output dropped off in 1932 as he moved to the fullback position. He appeared in 11 games and ranked sixth in the NFL with 375 rushing yards, but scored only 15 points on two touchdowns and three extra points. At the end of the 1932 season, the Stapletons team folded.

Answer this question "when did he sign with them?" by extracting the answer from the text above.
He played for the Stapletons for four years from 1929 to 1932.