Alex, FCTM just says:
With DERATE (ie 24K)
"If an engine failure occurs during takeoff, any thrust increase could result in loss of directional control"
with ATM (ie 26K 42°C)
"If more thrust is needed during ATM takeoff following an engine failure, thrust on the operating engine may be increased to full rated thrust by manually advancing thrust levers. This is because Takeoff speeds consider VMCg and VMCa at the full rated takeoff thrust."
with DERATE and ATM (ie 24K 32°C)
"If an engine failure occurs during takeoff, any thrust increase beyond the fixed derate limit could result in loss of directional control and should not be accomplished unless in the captain's opinion, terrain contact is imminent."