Restoring 8.0 db to 8.1

Hi

I am trying to upgrade my database from 8.0 to 8.1 and am looking for a
little info/advice.

This is a production database that we are migrating and it is in CONSTANT
use, so the maintenance window must be small and hopefully mostly off-hours.

We use a PITR/LVM snapshot solution for our backups and were hoping to
simply restore the filesystem and startup under 8.1. Obviously this didnt
work, and I know the doc says a conversion is necessary, however I havent
found anything with enough detail to sway me from a better solution than
pg_restore.

The problem with pg_restore is that our database takes 3+ weeks to restore
from a dump file. This is not an acceptable window for us. ( Approximately
3 days of this is data + lobs, and the rest indexes and constraints. If we
are doing something wrong here, I am all ears as well )

Could anyone point me to the information I am missing or offer some middle
ground solutions?

TIA

Bill