[Samba] NT groups vs Unix Groups

[Zylo]

Hello,

I'm not clear withs groups mapping between NT and Unix Groups.
Configuration :
PDC : NT4 box (PDC won't migrate to samba)
Samba 2.2.8a (UCLA binary) / AIX 5.2
Security = domain.

Some NT users and groups have more than 8 cars.
For the users, we have the "usermap" file, seems to work fine.
What is the solution for the groups ?

On the other hand, is the NT group membership enough, or shall I maintain
the groups memberships on both sides (NT and Unix) ? Tests I did let me
think that NT membership is enough, but docs on the web says the opposite.

Any help or good link is appreciated !

Thanx in advance.