For normal trail riding, the rear cinch isn't necessary. Many horses have never used one so be careful if you use yours and try your horse in a round pen or lunge line at all gaits before climbing on board.
I would also go to a thicker pad if you are going to do a lot of trail riding. My saddle was custom made and fits my horse wonderfully but I still use a 1", 5 Star pad. I primarily trail ride and we go out for a few hours on a lot of diverse trails.
Circle P is a rather low end saddle that is sold quite a bit on line or through many of the mail order stores. It isn't a saddle that I would put a great deal of time on. If you are going to be riding regularly for a few hours, there are better saddles. It isn't one of the worse - such as the starter saddles off ebay
- but it isn't a great deal better.