One thing most folks don't know about a shroud is the position where it needs to mount. The fan blade should have half its blades covered by the shroud. That usually means the back of the shroud should be approximately in line with the fan hub, so half the blade protrudes out the back. If the fan is totally enclosed, the shroud will actually restrict the airflow.
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!