The Flash Pair are 17 years old and both stand about 5'3" (give or take half an inch). It is less clear what their costumes should look like, since they differ considerably between the novels and the anime.
(left) color frontispiece for the Daatipea Flash manga by Makihara Hisato
(right) color frontispiece for the Daatipea Flash DX manga by Oono "Takemaru"
both were published in 1996