Things always go better after a "few" beers :)   (As it turns out I don't
really have an answer for you) BUT..

I recall, the IBM 3494 has reserved slots for "lost misplaced" tapes - the
homeless...  This slot needs to be kept spare. Plus one for cleaning tapes,
Customer Engineer Tapes etc ......

It never worried me much as the 3494 we had, had 2700 + slots... but on a
smaller Library I can see your getting anxious.

Could the above apply to the DELL maybe?

Regards