You can if you wish try using the complete JeeLib in the 3-phase sketch instead of the stripped-down part that is presently used. I cannot remember now the exact reason to moving to the stripped-down version.
I had something like that in the back of my mind, it was most probably the reason. And if that was correct, using JeeLib instead will fail. The present radio code is JeeLib except for a few lines courtesy of Martin Roberts and (from memory) one other change caused by a timing problem, but it does not have the receive code that would be required - which is most likely what caused the space problems if that was indeed the issue.
It may still be worth trying the full JeeLib - in the meantime, the Arduino IDE might have become more efficient in the optimisations it applies.
I changed the 3-phase firmware to use the jeelib and added the ACK-part and it seems to work quite well!
Not quite sure if the following define statements are still needed: