 This could, in fact, be adapted to more-or-less existing airframes, which the Soviets soon did, with the Sukhoi Su-17 (based on the earlier swept wing Sukhoi Su-7).The limitation of the wide spacing, however, was that it reduced the benefits of variable geometry as much as it reduced their technical difficulties.For the new, "clean-sheet" Soviet designs, TsAGI devised a more narrowly spaced arrangement similar to that of the F-111.