Box Building and WinISD beta

I am using WinISD beta to build a sealed angled box for a SVC 12" 4ohm Alumapro Alusonic.  They calculate an ideal volume of 1.18.  First, does the program already take into account the displacement of the driver.  My understanding of this driver was that it would need about 1.0 cu ft, so 1.18 ideal does not sound far off.  I would like to make the enclosure smaller and I have heard about using polyfill because it makes the enclosure perform as if it had a greater volume.  I understand how much to use per cu ft.  However, how do you know exactly how much larger it is making the enclosure?  Assuming you will stuff it, do you make the enclosure for .9 cu ft or 1 cu ft or something in between?  Also, does it matter which surface of the box the sub is mounted on?