In answer to the question...
I tried 12 MHz once during the day near the height of summer... and most of the listeners were unable to hear it, in the larger "blackout zone" around the transmitter site, that gets larger as the frequency gets higher. Think I had one logging on that frequency from Florida, and that was it.
The 6.9 range will work during the day, especially in the winter, but the maximum range will be less, and signal strength lower-- but that can be somewhat balanced out by lower noise.