This is how i would be in feral form.
i will explain you the reason why i am so big.

dark dragons like me are sons of a dragon and a wivern, the mix of the blood made this race to grow up really much more than other dragons, so if normal dragons are like 4 or 5 meters tall and 8 or 10 meters long, i am 21 meters tall and 40 long with 80 meters of wings in total when opened.