DS2:basing & measuring range

Other than for large and overlarge vehicles (heavy tanks, semi-trailer
cargo
carriers etc), I have been basing my units including infantry on 3cm (1
1/4") square bases. As there will be different basing conventions and
opponents with incompatible bases, how have members coped with this for
LOS
and range purposes.  Do people measure from base edge to base edge or as
I
will be doing, from centre of the base to opponents centre.  Vehicles
are
easy as it is model edge to edge but for infantry, measuring from the
centre
makes more sense.  Any advice appreciated.  Also, do most people have 4
stands per platoon/unit or 5?

regards
dave tan