What is the optimum throw distance?

I was going into the sharp software program to find out where to hang my new projector. They give me a maximum distance of 15.20ft and a minimum of 13.14ft. I have the option to place it anywhere between these two dimensions as I have just built a dedicated theatre, but what is the absoulute best position. Do I go with the minimum or the maximum?
I would say filling the screen is #1---Then you might need to zoom out for some material(that would be some of the quasi hd movies)to fill the screen. So, you need to be able to "over-fill" the 16x9 in order to be able to "zoom out to fill" 4x3 material.
Other things to consider are: angle, cabling, heat, noise and cone.
Optics and Geometry will be best near the center of the range (14ft). Keep in mind this is usually the distance from the screen to the front of the lens so mounting will be somewhat further than that. Lens is typically offset left or right so you need to compensate for that too.

Some projectors have offset too (distance from top of screen to lens height). Cheaper projectors usually have a fixed offset like 2". If you have zero offset than the projector lens center should be even with the top of your screen area. Sometimes projectors have offset that increases as you move the projector back. This is usually desirable because you can get the projector closer to the ceiling. Keystone adjustments can compensate for projector placement if your projector has them. I try and mount projectors as perfect as I can and then use adjustments to fine tune.

When calculating screen and projector positions I usually start at 36" off the floor for the bottom of the screen area. Then depending on screen size I now know my top of screen height. Add your projector offset and go from there. Depending on ceiling height you may need to adjust screen size or height off the floor to get things to fit within your requirements.
The best distance is to use NO zoom at all, i.e. as far back as possible. In your case, the front of the len should be 15.2' from the screen.

To prove if for yourself, just place it on table level and move the projector among those two points. Hope this help.
Thanks for all your responses , and all your help. I am now awaitin carpet install in the new year for the final set up.

Cheers and a happy new year to you !!!!

Can you explain further why no zoom would be best. I like your idea for experiment before installing.
For a high-gain (1.3) screen like my Stewart Firehawk, further back is better. The reason is as follows: A longer throw will minimize the angle of the light-cone, and this maximizes the reflected light back to the viewer positioned at zero degrees on-axis. In contrast, a shorter throw distance will maximize the light-cone angle and cause greater off-axis reflected light away from the on-axis viewer.

Secondly, a high-gain screen in particular (but any screen) will benefit from a ceiling-mounted projector positioned such that the viewer would "see it" in the center of the screen if the screen were considered to be a mirror. This way, the light from the ceiling-mounted projector reflects downwards, bouncing directly towards the viewer. In contrast, a low mount (as in a table-mount) will cause the light to bounce up towards the ceiling, away from the viewer.

I also have a Sharp projector. Ideally, the Sharp projectors should be mounted level in the horizontal plane, and at a height in which the lens is level with the top border of the screen. The vertical offset wheel should then be used to bring the picture down to fill the screen. It is not ideal to "point" the projector downward at an angle and then correct the distorted image using keystone. Try to avoid using keystone at all -- instead use proper initial positioning and the vertical offset wheel.