Jazty, that's pretty close to what was on the bus before I think. There is a J rail over the passenger door, and there used to be one just where yours is over the windows, but this one's roof got lifted and it was removed. With the lift, there is about 1 foot of new side between the top of the windows and the bottom of the roof curve.
The temptation right now is to first add something where the roof curve ends along the entire length of the bus. Then add a second channel just over the windows. The redundancy might help a bit more to keep water from running across the windows.