I made a spraybar return for my 75 and I drilled two rows of holes: one pointed forward and up and the other pointed forward and down. I'm runnign two Rio 2500s into it and I think my spraybar is about 24" long. (I didn't really measure. I just made it go as far across the back as I could.) Mt thought was to both create some surface turbulance and to create a current around the live rock. This is also supplemented by two Maxi-jet Pro 600s set at opposite ends of the tank in the circulation pump configuration. One points at the front of the tank and the other points at the back. I figure I have kind of a cirular flow the way my rock is stacked.
The picture below isn't terribly recent, but I think it will give you the idea.