IBM says I have to power off the Guest to remove the 17th space.
There's nothing in their code to stop a 17th space on a NWSD that won't
play well with it. IOW, it doesn't check the NWSD type on ADDNWSSTGL.
Apparently this limitation doesn't apply to all NWSD types.
I guess that 140GB will stay wasted until I can IPL the guest.
Submitting a DCR.