Daenerys Targaryen's dragons gradually increase in size over the course of Game of Thrones (the TV series), and Drogon seems to be the largest.
At the end of season 7 (episodes 6 or 7, shouldn't matter really), how does Drogon's size compare to Balerion the black dread, Aegon I's dragon? Also, is its growth known to have/have not stopped?