There is a chance you will need more than one on a 24" tank. I had to add a second hydra52 after a year to deal with shading. From what I have seen neither the Radions or the Hydras cover 24" in the short axis, especially if you have any kind of steepness in your scape..
I agree it could be and I certainly remember your glorious tank -- But I don't think it's completely necessary, I think shading is better combatted by supplemental LED's at an angle.
- In the back at an angle like a back slash /
- In the front at an angle like a forward slash \
The issue with shading is people keep trying to take a light source which is nearly 100% on the Y (vertical) axis and have it apply to the X (horizontal) axis -- Basically, force it to do something it's not good at doing. When tilting the light will give you what you desire while allowing the LED's to function as intended.
There's a member here (Silef, I think) who has a beautiful SPS dominated tank lit by Kessils only. He achieves this growth by doing what I had said A row of Kessils in the front facing the back (4) and a row of kessils in the back facing forward (4). I achieves this with 8 Kessils on an 8' tank.