> Any other ideas?

First of all, you didn't answer about forced writes =0.
This parameter is specific to the database
(like page size, sql dialect, sweep interval, buffer pages).

So, other ideas (from these parameters):

1. forced writes=0;
2. sweep interval=0;
3. buffer pages...let's say 8192
4. force some 'expansion' of the database file by inserting
a large number of rows and then deleting them ...that would
insure enough free space and avoid any requests to the OS
to allocate more space to database...

Change parameters 1..3 with IBAccess/IBExpert/IBConsole
and please post the results of your test....

Tiberiu