[Users] Pools and pre-started VM in 3.2

Hello, f18 node + f18 engine, both in 3.2 final. If I create a pool, the "prestarted VM" field is grayed out. See: https://docs.google.com/file/d/0BwoPbcrMv8mvN3d2a0drb0szYk0/edit?usp=sharing After creation of this 5-VM pool, I can go and edit it and set 2 in prestarted field, and after several seconds 2 VM are correctly started by engine. Do I have to configure any engine parameter to be able to set prestarted VM at pool creation? Or is this the expected behavior to set only on edit? Thanks, Gianluca