If you can hang it anywhere you want...
Hang it towards the back of the range that is allowed. As stated above, throw distance is supposed to be from the front of the lens always. So, you want to measure from the center of the mount to the front of the lens and add that distance to your calculation for where the mount goes.
Why the back of the range? Well, the further back the projector is, the more you have to zoom in to fill the screen. This decreases the angle that the light is coming out of the projector. Therefore, the light hitting the screen is doing so at less of an angle and will reflect off the screen to viewers at less of an angle.
This will help to create a more uniform image for all viewers.
You don't want to be all the way at the extreme end of the zoom (either way) as the possibility exists that there will be some distortion in the image caused by the lens and poor optics. There is never a guarantee that this will happen, but the chance exists, so I just avoid it on prinicple.