I'd agree with jyl... there will be some forward shift of COG, but maybe not enough to help the saddle. You might end up with neck and shoulder issues, or you might not. It is not generally recommended to try to increase the weight that your shoulders and arms are supporting.

I'm curious, though: where is your seatpost attached to the saddle? Is the saddle all the way back? Centered? If the saddle is all the way back, that can certainly generate very large bending stresses on saddle rails. Especially if you stay firmly in the saddle for rougher parts of riding.