Placing the pump in opposite sides is the best way to get flow into the tank. In terms of the sand storm, you will need to play with flow patterns and intensities. Flow is very subjective and what may seem like too much flow for someone may not be enough for others. Every tank is different so what works for you may not work for someone else. In this case, I wish there was a straight answer but there isn't. The only thing we can offer is for you to continue testing until you find something that is ideal for you and your corals.