ORIGINAL: Wheelnut
In addition to the heat sinc cooling it looks like you could get a couple of turns of some water cooling coil near the brushes which is where the heat comes from. Thats a tough one. I would run it and see how hot it gets with the cooling you had on it. If it gets too hot you might want to consider changing the motor mount.
No.it doesn't matter. air cooling does a better job then water cooling any day !