As others have said, it really doesn't matter that much. Go to the fields you are going to fly at and keep an eye on the channels in use, and pick the channel that has the fewest users on it. Although, that can change too. I originally started on channel 56 because there was nobody else on it, but now there are 5 of us using that channel.

As far as high/low with Futaba radios, not all manufacturers do that. I fly Airtronics and with those you can put any channel in a reciever, there is no high/low with those.

Ken