In the May issue of NEWS/400, Jeff Tenner wrote an article on the topic you ask about called, "Boost Domino Storage Capacity." You can also see a longer version of the article online at http://www.news400.com/bonusfeature/1999/May/Tenner/5258.htm. Jeff is using the concept to store Domino databases in a user ASP with hardware disk compression to save space. I believe what he describes would apply to your situation.
Jeff describes two steps. First, you create a user defined file system with the CRTUDFS command. Here's the command he uses in the article:
CRTUDFS UDFS('/dev/qasp03/Domino1.udfs') DTAAUT(*EXCLUDE) OBJAUT(*NONE)
The qasp03 is the third user asp; in your case, you'd use qasp02. The second step is to associate the UDFS with an IFS directory using the MOUNT command. Here's the command as Jeff uses it in the article:
MOUNT TYPE(*UDFS) MSF('/dev/qasp03/Domino1.udfs') MNTOVRDIR('/notes/data/archives')
I hope you find his article helpful.