Speaker placement and repair

Two questions:

First, I am trying to arrange my Meadowlark Ospreys in a room that is 12' across (sidewall to sidewall) and 19' front to back. On one side wall, I have bookcases that are 10' deep. For purposes of placement, do I measure wall to wall, or wall to bookcase?

Second, the cone center fell off of the bass on one of the ospreys. What kind of adhesive should I use to replace it?

Also, anyone who has learned special voodoo of placing the ospreys, input welcome.

TIA.