There's a pic of a 1.8 cm tabanid at the link, below. Tabanids
include horseflies which are the heaviest of the flies.
If you are looking for a fly that covers a lot of real estate,
the Tipulids or crane flies have legs that reach a maximum span in
tropical species of upwards to 10 cm. They are very spindly and
would not approach the weight of a big tabanid.