you're thinking of putting a ray in a 24" wide tank for life, when that ray's disc will potentially get to 11"+, and you're not factoring in the added tail that will be equal to or longer than the disc is in diameter.
a reticulated ray generally has a longer tail than its disc is, a 7" disc is looking at an 11" or so tail.
they wouldn't be able to turn very well in a 24" tank. not for life. sorry to burst your bubble.
Just to get more width and length. Still want to be able to keep other species of fish so i dont want to go lower. If the ray was the only fish in the tank, would a 72x24 be ok? are hysrix or retics smaller? I want the smallest species possible that i can find. Already found both.