2KB is the most the SD will be using at any given time, but I'm not sure under what conditions that would be. However, since the call stack is being shared between the application and softdevice, the maxium usage should be determined by doing a new stack analysis with your application FW. One way of doing that is to "paint" the stack with a known pattern, then read the stack after running your tests to see how low the stack pointer was at its lowest.
Granted one can do a stack analysis, however, given a fixed set of timers/queue sizes etc, what is the soft device component that uses the most stack? ble gatt, ant? ble+ant?
