But it has put a higher floor on CFC's potential price decline, even if it's only a couple of bucks.

There is no higher floor due to that deal. It just gave BAC a security net and shorting opportunity on their investment. Remember they get preferred shares so they get the goods first in a liquidation pulling the floor out from under the common shareholder. They just screwed the longs and for that put a lower price floor on a BK.