Thanks to everybody who helped out today.  The Db extend went great and was
actually quicker than doing this with a jfs file system because you don't
have to do a dsmfmt.
Here are the steps I took:

chose 2 stg vols on different disks.

made sure no sessions or processes were active that could affect those vols

performed a move data on both vols

varied both vols offline

matched vols in ADSM with those in AIX and took note

deleted both vols from ADSM

In Smitty I was able to rename both vols instead of deleting them

Added the new vols back into ADSM
if you ever do this make sure you name the new vol with a leading "r"  This
is nessasary to let ADSM know that it is a raw volume.
example:  /dev/radsm_db4

performed an extend DB

:-)