Flow rate does not necessarily control how frags will grow straight or not. Actually, flow determines how thick the vertical branches will be. The stronger the current, the thicker the branches will be as the coral will need to adapt to the increased flow if it wants to grow toward the light source. Corals like terrestrial plants, will grow in the direction of the light source. This is why some reefers, including myself, will sometimes angle the light toward the corals in the front. This will entice the frags to grow toward the glass, giving you an almost topside view of the colony. There was a reefer in Germany or Europe that talked about this concept in either a Reef Hobbyist or Coral magazine last year I think.

I wanted to go the route of a SCWD but heard and read a lot of bad reviews about the device stalling or stopping due to build up or something. Still a great product, you just need to be on top of maintenance. In my own tank, I run (2) MP40's and (2) Jebao WP45's with a SICCE 4.0 return pump. I'm thinking about adding some gyres as well to totally kill dead spots and increase the overall flow in my tank. I have sand but only an inch or so, which I have to be cognisant when I play with my flow.