Sybyl FF followon

This is in response to a posting "Sybyl FF followon"
 >2) What is a reasonable cutoff - the paper lists 8 A, but should
    this be lower/higher?
 I guess One has to fix the cutoff depending on the density of the
 system. In a low density system with 8A cutoff, a molecule may just
 see the nearest neighbours only.