determining max_fsm_pages

Pg: 7.4.5
8G ram
200G RAID5

I have my fsm set as such:
max_fsm_pages = 300000 # min max_fsm_relations*16, 6 bytes each
max_fsm_relations = 500 # min 100, ~50 bytes each

I just did a vacuum full on one table and saw this result:
INFO: analyzing "cdm.cdm_fed_agg_purch"
INFO: "cdm_fed_agg_purch": 667815 pages, 3000 rows sampled, 52089570
estimated total rows

My question is this: I have about 8 databases running on this server.
When I do a vacuum full on each of these databases, there is a INFO
section that I assume is the total pages used for that database. Should
add ALL these individual pages together and pad the total and use this
as my new max_fsm_pages? Should I do the same thing with max_fsm_relations?

TIA
Patrick