I am trying to determine whether a HF radio is needed for a flight from Panama City, Panama to Nassau, Bahamas. The route takes you over water fro 570 miles. Flying a 25,000 feet. I am trying to figure out how far can you go with only VHF. FAR 91.511 states I can do it as long as I am not without VHF communication for more than 30 minutes. thoughts?