That's similar to the halfway setup I had before I added the second pair. A ss18 on each side of the overflow (west end) mounted low with the xf150 high on the east end. Created a good gyre type flow regime across the tank. Little bit of dead zones around the lower rockwork on the east end but that's mostly due to how the sand drifted on me. I'd recommend aiming the ss18s just above level if you have fine sand like me. Keeps the lower edge of the cone close the parallel with the bottom of the tank . I also try to keep them about a foot off the bottom... "Try" being key here.Glad to hear as I’ve been eyeing a set of 4 for my 600 build. My thoughts are to put them down low and put 1 Maxspect XF350 on each end up high.
Ive now effectively replaced the gyre with a second pair of ss18s aimed slightly high since I have some surface film issues. Works pretty well, just have to sort the dead spots when I redo the rockwork over the next few months.
I will also mention that mounting the ss18s on 3/4" glass is a bit tricky because the magnetic field doesn't reach much beyond that. There was lots of falling off the glass followed by some cursing because my tank layout makes positioning solo very hard... Bring a friend and its not bad at all aside from figuring out how to get them to rotate right.
Id also let them hang by the cord before installing to let the cord straighten out. If it kinked the wrong way in the box, it can be a bit unsightly and makes aiming harder too. One of mine has a lot of cord in the water because I didn't do this.
One other little note, the light sensor for the night mode is on the controller. Some of the videos make it seem like it's a remote sensor but it's not. Thought I'd share since I was surprised by it.