Mountain bicycles tires?

I have a Felt NINE elite 2008 the frame fits me fine but the height is a bit too big since it has 29" wheels. Would it be a bad idea to mount a set of hybrid tires to the original rims on this type of bike? That would make the bike's top tube over inch shorter which would be where I need it. This bike is... show more I have a Felt NINE elite 2008 the frame fits me fine but the height is a bit too big since it has 29" wheels. Would it be a bad idea to mount a set of hybrid tires to the original rims on this type of bike? That would make the bike's top tube over inch shorter which would be where I need it. This bike is considered a medium level mountain bike. I will be loosing the aggressive knobby tires and the new ones would be quite a bit narrow.
Update: The frame is 17.5" which is rather small and fits me right. I do have clearance but I want just little more so I can maneuver the bike better,
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