Experimentation is your only sure answer. The strength of the radio signals is affected by distance and the composition of anything that they must penetrate through. It could be that the signal path through the wall(s) and ceiling(s)/floor(s) is better with a high angle or a low angle. You can't really know until you try. If your best signal is still on the weak side, consider a reflector like the ones described at http://www.freeantennas.com/ .