 However, he continued to be active in aeronautical design, a 1966 paper challenging the view that tactical aircraft necessarily required greater and greater speed to be effective, and proposing a close air support aircraft armed with a heavy gun for anti-tank operations to Martin management, which was not pursued.In 1974, Multhopp's son, also named Hans, invented "Checkers chess", a chess variant in which pieces cannot move backwards until they have reached the far side of the board (another game by the same name was proposed by V. R. Parton).In 2014 at the age of 59, Hans won the Ohio Championship.