samba - Jul 2012 - Config doubt

Hello all.

Is it right to have:
        idmap backend = tdb
        idmap uid = 2000-9999
        idmap gid = 2000-9999
        idmap config PERSONALE:backend = rid
        idmap config PERSONALE:base_rid  = 500
        idmap config PERSONALE:range = 100000 - 49999999
        idmap config STUDENTI:backend = rid
        idmap config STUDENTI:base_rid  = 500
        idmap config STUDENTI:range = 50000000 - 99999999
in smb.conf to use the given ranges for PERSONALE and STUDENTI,
reserving the (small) range 2000-9999 for every other domain?

I'm only interested in users and groups from the two "big"
domains, but
I've had clashes with groups in another domain making "id
user.name"
return numeric-only GIDs (since they mapped to two different groups in
two domains).

If it's the wrong solution, which is the right one (except defining a
range for every domain in the forest: I can't do that)?

Tks,
 Diego.