They had plans for larger ones...
...but a few of these actually "flew". From EKRANOPLANES
"'Volga' in 1963 was constructed the huge (length 348-ft, span 131-ft, weight Loaded - 1091,000-lb) ekranoplane KM ("Korabl-Maket" (ship - model"), received the NATO nickname "Kaspian Monster". It was the largest and heavy flying apparatus in the world."