Memory Requirement for Mesh Network

I am using XBee S2C.

We are closing on the hardware design and deciding on whether we need 256KB of Flash or 128KB Flash is enough on the micro controller for our design. One of the items we need to figure out to answer this question is that what is the memory requirement on a Router Xbee microcontroller if it is the parent of 20 End Devices (ED).

This is how I calculate the memory requirement on the Router XBee microncontroller.

-XBee routers that act as the parent to end devices generally store only a single message
-1 message is 80Bytes payload + some header bytes = 100 bytes?
-The Router should have storage for all of its ED - e.g. 20 in this case
-So the storage requirement in the Router is ~ 20 X 100B = 2000B=20KB

Does this sound good?

Why are you worrying about memory for entries in an End device child table? That is something that is within the radios firmware and you do not need to worry about it.