Jamie:
Do you have any of those metal minnow traps? If you do, catch a few BG and put some in each trap. Close the entrances, suspend them beneath a bleach bottle or something else at the various depths for a day. Pull them up and see if the BG are still alive. If so, then you probably have enough DO at those depths for a trout to survive, if they are dead, then definately a trout wouldn't survive.
Don't use FHM, they can survive low DO that would kill a trout.
I'm only suggesting that because you don't have an O2 tester. While the temps you are seeing are O.K. as long as the heat doesn't come back, you don't know if you have enough DO for the trout.
