I hold been using NVIS for local MARS HF operation. Right now FOF2 is running approximately 4 MHz to 6MHz by day and 4MHz to 2MHz buy night. FOF2 is the highest frequency you can sprint where the sign will fade straight up and come down. It changes with latitude,time of day and sunspot numbers. 200 KHz can make a big difference during day light hours. For myself I expend the data from Alpena, MI. Google real time FOF2 to find a list of sights near you for data.
On 80 and 60 meters I find a dipole at 16 feet to work best. excellent luck and excellent hunting.
Source: thesurvivalpodcast.com