I tried the controller-in-bag thing too, with The Velcro Eclipse,
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=20595
and even with the endplates off of the controller, it still got too warm for my liking, even with the end flap of the bag open, facing forward, with all the airflow that gets.
That was with the 9C on there; I expect using the Fusin controller and motor that way will probably be less heat, at the same 36V, but I don't know yet.
I had first tested it without a bag, like this:
and had no problems.
After that I stuffed it all in the bag and tried it out, and that's when it was too warm for my liking. I can't seem to find the pic of that.
Finally, it was like this:
and that ran even cooler than the first way, since the controller had it's open ends along the direction of airflow. Not a lot of testing that way, though, as I didnt' end up getting very much riding done on TVE, before I wound up putting the motor back on DGA and then on CB2, IIRC.
Unless the fan either pulls air *thru* the controller, with the ends off or ventilated, or else pulls air around all sides of the controller from outside the bag, with airflow at least equivalent to what it would get if it werent' in the bag, it probably won't make much internal temperature difference from how you are doing it now with the bag partly open.
And unless you use a squirrel-cage fan, it probably won't move enough air for a really small size, either.
All the tiny axial-flow fans I've used that are not incredibly loud and power-hungry (and even most of those) move hardly any air if there is anything at all impeding the flow, either into or out of them. On their own, with nothing behind or in front of them they can move a lot of air, sometimes, but not once the flow becomes turbulent around them, like when air is passing over components and stuff.
The radial-flow fans (squirrel-cage) usually move way more air for the same power and noise and size, with the change that the airflow is now being redirected 90 degrees. That might actually be better, in the case of the controller-in-bag, as you could make the exit port at the corner zipper point, perhaps, so that it can still be only unzipped a little during use, and the inlet of the fan at the end of the controller, with the other end open completely for best airflow. If the bag itself has a water-resistant liner, it is also going to stop airflow, so you would either have to open the other end of the bag, too, or install a hidden vent somewhere, preferably near where the other end of the controller is. If the bag is cloth only, the weave may let enough air in over it's entire surface area to be rather like the opposite of a vacuum-cleaner bag (whcih inputs at the hole, and exhausts thru the rest of the surface area). Caveat: The outside of the bag will get dust sucked into the weave, this way.
