On the subject of tire pressure on gravel, I would actually DECREASE your pressure for better performance and puncture protection on gravel. Lower tire pressure will help take some strain off the suspension and make the tire less prone to puncture by allowing them to flex more.
I have found LT C tires to be perfectly adequate on gravel roads in rural SK but 10 ply LT E tires are more suitable to crushed rock roads of the north where I was getting a flat a week on my 6 plys.
If you aren't getting flats though I wouldn't worry about your tire choice, especially if you are carrying a full sized spare, a good patch kit and compressor (which IMO should be compulsory equipment for anyone traveling off the black top or in rural areas).
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