Even a slightly out-of-balance fan is dangerous. Doing any trimming at all on fan blades is a recipie for disaster. There are several types of aftermarket fans designed to fit a variety of applications, but use then "as is", with no modifications. Spacers between the fan and the pulley are OK, trimming the diameter isn't!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!