I have a sag in my floor that drops 1-3/8" toward the center of the room. Leveling compound, I have been told, is typically used for up to 1/4" difference in floor level. Someone told me to place center post under the floor- only this floor renovation is occurring over the garage and placing a center post in the garage is not recommended for obvious reasons. I am out of ideas any help or suggestions would be greatly appreciated.