You can, yes.  I copied the wording on mine from examples found directly in the book, and the exact wording actually says to 'ignore Physical Stress or Trauma results'.  The regular Immunity SFX doesn't have that wording, but also doesn't mention anything about timing at all, so I'd assume it can probably be activated the same way.  It's actually fairly accurate to the way fights tend to work in comics, really.  Characters with total physical invulnerability often tend to get taken out by either complications, or attacks that would count as hitting one of their other stress tracks.<br/><br/>Though, now that I think about it, it may be a good idea to alter Ace's Venusite Poisoning Limit so that it also shuts down her Venusian Invulnerability SFX, since the limit already shuts down her Durability power trait.  Otherwise, things could get a bit weird from both a mechanical and a narrative standpoint.