Tape drive configuration suggestions

Here goes with a vague question....

I have a customer with an 820 with just short of 300 gigabytes of disk
currently being backed up to 3570 B1 using BRMS/TSM combination. They also
have a 720 with a similar amount of disk and tape drive, used as a
development machine and a standby DR machine. This second machine will in
the future some time probably be upgraded to an 820 and is almost certain
to act as a data replication point for the primary production machine.
These things are just a matter of when not if according to the customer.
Obviously the disk will grow and 500 gigabyte data quantities are not that
far off as is some kind of near 24/7 operation.

The customer has been talking to IBM about how to proceed with upgrading
their tape devices and the long and short of it is that there seems to be
some confusion as to what is a good upgrade plan strategy taking into
account their current configuration. I believe the 3584 was recommended but
then seen as a likely bottleneck.

Without a lot of thought my suggestion to the customer was to get a
smallish LTO on the prod box to be used for tape backup and restore in the
immediate future, and down the track for those one-off events and tape
transfers, and a larger LTO on the dev/back-up box where the major tape
work is likely to be conducted when they get their replication in place.

What general (or specific) suggestions does anyone have about
configurations and hardware they use for similar setups and why ? Anyone
got any good thoughts, questions, ideas, things they wouldn't do again to
share ?

Any response appreciated

Regards
Evan Harris