K800 J-head retainer for suspended fun duct

I hade an problem as fun duct was 5mm too high.
Instead to cool prints, it cools just heater.
Also I could not set it in position that do not touch towers at closest coordinates (ex. X0 Y90 touch tower and effector slip from magnets).

With this modification, fun duct is 5mm lower and there is 5mm space for screw head so it can be mounted not to touch towers in max position.