I use 2mm pencil jets & i prefere the position of the jets more towards the edges of the brush. I see some jetted just either side of the brush neck- totally useless IMO as you will get no flow at the edges. To give you an idea of my prefered flow rate, if you lay pole on ground with jets pointing upwards, the water would reach approx 18" high before tailing off.
P.S. i don't like fans.
Tony