I shot one of these a couple months ago. I cheated (used a bobsled), but I was the only one shooting the class, so... I took my service rifle, stuck a bipod on it and went to the match. That's it. I used a bean bag for a rear bag.
Two initial thoughts: First, the bob sled should be allowed. More specifically, you should be able to take a legal service rifle, put a bipod on it and be legal (and competitive).
Second, I shot at mid range (600 yards). I'm classified as a High Master in Mid Range F Class for reference. I shot a 583 on the big (sling) target. It would have been a 531 on the F Class target. Wind was light to moderate, and I had never shot this rifle off a bipod prior to the match (it's my service rifle gun), and I have never worked up a load for it. I just put a 77 on top of some varget and called it good. Long story short, the F Class target will be punishing, but I'm not sure the sling target is small enough- shooting in the 580s on your first outing while only taking it semi-seriously seems a tad too easy.
All that said, it was amazingly fun. It's like F Class without having to worry about working up a load.