Have you already considered using/misusing VOLUTIL CONTIGVOL for this
adventure? I vaguely recall that it has some option to force it moving
the extents on the same drive or allow it to shovel extents to other
drives (if the volume restrictions of the file permit this).

The VOLUTIL SHOWUSAGE command may also be helpful in getting info about
the extent distribution of your drives (i.e. which file has extents on
which LDEV).

Lars (no VOLUTIL HELP or LaserROM available at home)