Originally Posted by Ridin' Green
a humped blade serves three purposes that I am currently aware of. One is to help protect the spindle bolt by mere the fact that it is recessed in relationship to the cutting edges/height. If they'll clear, so will the spindle bolt (as in going on or off the trailer or over a root, shallow small stumpe etc). Also, a spindle designed to run flat blades has to be longer to keep the blade in the lower part of the deck where most machines run their blades.
The main reason though is to help eliminate the drag on the grass surface by the entire length of the blade which can only reduce power, and cause extra wear to the spindle bearings.
I guess I can see the spindle bolt protection but the drag issue I've heard and dispute. If the deck pitch is set correctly the front is lower than the rear so in most cases the grass is cut to length prior to the rest of the blade coming in contact with any grass. This would also keep added stress of the spindle. IMO the added lift gained from a flat blade would out weigh the possible damage to the spindle bolt.
The X-Factor blade hump is so minimal that I don't know if it helps much even for your purposes stated. You can see pics of the oem blades here.