PITR - "Rewind to snapshot" scheme

I have been following and experimenting a bit with PITR for a while,
and I wonder whether it is practical to use the PITR hooks to roll
back the database to a known state. The scenario is that I am
developing a script that will be massaging data in a medium size
database. A pg_restore of the pristine data takes ~35 minutes to
complete, if I can take a snapshot right after pg_restore, and use it
to later "rewind" to that point, I'll save 35 minutes every time I
need to test it.

The dev box where Pg runs has plenty of disk space to spare - and
it'll be a dedicated Pg instance. I've already raised wal_buffers to
20000 and also disabled wal fsync.

So my back-of-the-envelope plan is to

- run pg_restore
- setup wal archiving so that the logs aren't deleted
- pg_start_backup('label'); cp -pr pgdata pgdata-snapshot ;
pg_stop_backup('label')
- somehow remeber the transaction identifier

At this stage, I can run my data-garbling script, and to "rewind" I
should be able to

- stop Pg
- install an appropriate restore.conf that stops at the correct
transaction identifier
- cp -pr pgdata-snapshot pgdata
- start Pg

Would something like this work? My only worries at the moment seem trivial:

- getting the transaction identifier
- pruning the non-current timelines to avoid the archived logfiles
from eating me alive

cheers

martin