Finetuning Autovacuum

PostgreSQL 8.4/FreeBSD 7.2 amd64

I have a database which has 3 tables which get a very high level of
activity (about 40 thousand updates per minute).

The tables are getting quite bloated, since autovacuum is apparently not
optimally configured (it is using the default settings).

Anything I do must be such that it will not cause deadlocks, since the
effects can be catastrophic with the amount of data being pumped through
the system.

Initially, I had scheduled tasks through pgagent running a vacuum
analyze every 15 minutes, but other posts I have read here have stated
this could cause deadlocks, and mentioned running autovacuum is
preferable

.

Also, are rows "vacuumed" in the indices made available without having
to reindex? The reason I am asking is because the indices seem to be
bloating to a much higher factor than the data table.

Thanks in advance