Cisco Cisco IOS Software Release 12.0(13)S7

Use the command bfrp carve-level 1 to selectively disable buffer recarve, by allowing recarves only for 
maximum slot MTU changes.

Use the command no bfrp carve-level to restore to default carving mechanism.

At any given time, only one of the two buffer levels (carve level 0 or carve level 1) can be activated.