I have also tried the following using only firebird 2 gbak:

$ /opt/firebird/bin/gbak FB_1.5.FDB -B BACKUP.FBK -user sysdba
-password masterkey;
$ /opt/firebird/bin/gbak BACKUP.FBK -C NEW_FB2.FDB -user sysdba
-password masterkey;

Then once logging onto NEW_FB2.FDB:
using a table such as
tbl(
column1 varchar(255)
column2 varchar(20)
)
create index BLAH on tbl(column1,column2)

and got:
Statement failed, SQLCODE = -607
unsuccessful metadata update
-key size exceeds implementation restriction for index "TEST"

--- In firebird-support@yahoogroups.com, "Lundy_no1" <Lundy_69@...> wrote:
>
> Yeah, did the backup with firebird >gbak 1.5 and the restore with
> firebird2 > gbak.
>
> The database runs, but new features like long indexing dont work
>
> --- In firebird-support@yahoogroups.com, "Martijn Tonies"
> <m.tonies@> wrote:
> >
> >
> >
> > > This is probably a really stupid question, but I have a current
> > > Firebird 1.5 database and I want to migrate it to version 2. Now
> > > Firebird version 2 can run it, but it doens't seem to run in fb2
mode
> > > completely.
> > >
> > > For example im still limited to indexes < 255.
> > >
> >
> > Did you do a backup with Firebird 1.5 and restore in in Fb 2?
> >
> > Martijn Tonies
> > Database Workbench - tool for InterBase, Firebird, MySQL, NexusDB,
> Oracle &
> > MS SQL Server
> > Upscene Productions
> > http://www.upscene.com
> > My thoughts:
> > http://blog.upscene.com/martijn/
> > Database development questions? Check the forum!
> > http://www.databasedevelopmentforum.com
> >
>