LOLHaha, you're welcome :)
You are responsible for making me scratching my head for
15minutes trying to find what the heck this hint is and what it does ;-)!
It was good one!
As I had never heard of the 'fast full scan', I thought that someone was really REALLY trying to convice the cbo of taking the index :)
select /*+ index_FFS(t, t_pk) */ c1 from t where ...