Answer from Praveen Bhargav, Trustee, Wildlife First:
A buffer need not surround the Core. Any forest area adjacent to a Tiger Reserve can be notified as a buffer area, including areas that form a viable corridor connecting to another Reserve. For example, a notified Reserved Forest or wooded government land could be declared as a buffer area. After the recent Supreme Court Order the process to notify such areas is on and you could present your suggestions to the Field Director of the Tiger Reserve.