The only advice that matters is that of the engine manufacuturer. Provide them all the details and follow their recommendations to the letter. Failure to do so will risk the life of anyone subsequently operating the aircraft.
FOD and overtemperature are not the only terms of the equation. Much of the stresses in a turbine engine occur during start and shutdown. Starting with an inlet cover disturbs the delicate balance of air and creates situations that may lead to significant fatigue related failures.
Starting an engine with inlet covers installed is something the happens more than you might believe.