By August the water will probably be way down, which can make it challenging to lug a boat down to the edge. I've used the old mini-troll w/ wedding ring/maggot/white corn combo and done well on kokes there, I don't see why your fly wouldn't work too. The bite is normally first and last ligt of the day for an hour or so. Often in the midday, it's too windy to fish anyway. Go up in the hills and pick huckleberries in the afternoon!

Most of the fish I have caught there have been on the small side, but I have seen some nice catches come from the lake, and have seen some really big kokes up the Kachess River in the pool by the first big waterfall. This is closed water I think. Good Luck!