Locals do catch browns in the four-pound range and the river does hold browns ever bigger than that. Baetis, pale morning duns, caddis, stonefly. Try Pale Morning Duns in the afternoon and Caddis patterns in the late afternoons and evenings. You'll see caddis come off all day on cloudy days. Terrestrials play an important part of fly selection.
Ants are effective as well.
For attractors, try Royal Wulffs and Humpies. In Logan, most of the public water is artificial flies and lures only. The trout limit is four from Card Canyon Bridge downstream. Private water is well-marked. Anglers will also find nice accommodations in Logan.