I appreciate seeing the reasoning. Thanks to all.
My AFM does not have any guidance on takeoff performance with anti ice on. It has no guidance on the use of the ice vanes on the ground, and has nothing on the use of ice vanes on gravel surfaces.
We generally operate at ISA or below, even in the summer, and are never temperature limited on takeoff, always Torque.
I do see a significant effect on torque and ITT when I open or close these ice vanes after takeoff with climb power set, so the increase in temperature is something to keep in mind since engines generally last longer if they are operated at lower temps.
Here is another question: would the engine temps be higher if they were started with the ice vanes open (handle pulled out)?