If you use the RMS mounts and put them on the ends of the tank, you can pull the rail and RMS mount together so there is tension that will keep them in place,,,, mostly.I am looking at this for an 84" tank and assuming the 80.5" track will work for that application. Looks like it will need some reinforcement as mentioned in other posts. I am planning 4 XR30's and they weigh 4.5 pounds each. Seems like a lot of weight over that distance. One thing I am not crazy about is them just sitting on the eurobrace with nothing holding them on. One bump would send them into the tank I am afraid. Is anyone else using them and is this an issue?
I had that setup on my 72" tank with 4 gen 3's. One day I was standing on a chair over the tank trying to reach the back bottom of my tank ( 30" wide and 25" deep), when my shoulder bumped the rail with the 4 gen 3's on it and it fell over into the water. It was the middle of the day and the lights were on. 3 of the 4 lights shorted out immediately, and in the 20 seconds or so it took to pull them from the water and shut off the circuit, the 4th went out.
So while it is a easy way to set them up on a eurobraced tank, it's not the safest.
I wouldn't use the RMS brackets ever again.