AIX tape parameters

Hi. If you're running AIX,please read on. One of the more interesting things I've had to deal with of late is the 8mm DAT drive in an RS6000. As it turns out, the previous DBA had set the block size to 512K in onconfig. Unfortunately, the system administrator set the block size in smit to 1024K. This led to a great deal of fun and games when the database recently went south on us until we figured out how to recover (with MUCH thanks to Morey (sp?) in Lenexa support). Most places where I've worked on RS6000 equipment before set the block size at the OS level as 0 (variable length). I'm wanting to set the block size to 0, and the admin says no can do...his backups depend on it. What does your site use? Thanks, David