Yes it's OK to 'use'Flex/reduced' thrust now!origininally the flex was disallowed by certain carriers,same as in reduced VIS' case.
The other concern was the Takeoff speed requirement with the use of type 4(heavy)anti-icing fluid.(disallowed on some turboProps as the VR wasn't high enough to shed the fluid)
But the Industry seemed to have adopted the Flex'with deicing as a 'norm'
