Not a good idea. You may overstress the motor and damage the fan. You may also put too much weight on the mount. It is hard to duplicate fanblades and make them yourself, so they might not be aerodynamic and cause the fan to be noisy.
You might also endanger yourself or your family. If I were you, I would use the fan the way it is or buy a new 56″ fan. New fans are very reasonable and you may like its design, style, and color more I think you can get a premium quality 56″ ceiling fan for about $30.
Hope This Helps.