I know the question has been asked and answered if the 400 feet max altitude is a guide or law. All answers here on the forum have stated it is a guideline. My FAA B4U Fly App has me more than five mikes from my closeest manned tower (11 mi.)airport but within 5 miles of a small municipal airport, hospital trauma center and two other private heliports. The App says I must notify the control tower prior to flying. (It would be nice if the FAA INCLUDED THE NUMBER TO CALL.). Anyway I called the manned airport tower which is about eleven miles away and asked them what should I do. The gentleman was very nice and advised I should call them any time I wanted to fly so they could advise any local air traffic. He said to make sure I kept it at under 400 feet. I said I thought 400 feet was a guideline and not law and he disagreed saying it was a regulation?????