Three things can happen when your reel is not fully spooled:
RHINO fishing reel RCS5
Reel Fishing III happened in 2003.
Reel Fishing Challenge happened in 2009.
Reel Fishing II happened in 2000.
It's possible but the reel and rod are not made to handle the stresses that monofilament fishing line will put on the gear. The drags on a fly fishing reel are not as robust as a conventional reel.
Reel Fishing III was created on 2003-06-26.