Gray water holding tank leaks through crack

I've tried to sift through the other threads out there but can't find a definitive and best solution for my gray water holding tank crack.

I just purchased a 2007 2720. It has a crack about 1" long in the center of the tank running iside the indented rib recess. Although, the crack can barely be seen, the water easily comes out as it fills up. As a side note, the level indicators are suck on 3/4 full with the tank empty.

I've read that replacing the tank requires that the trailor be towed back to the factory and the bathtub and tank be rebuilt. This isn't practical.

The bottom of the tank looks like it is vacuum formed ABS. So, the inside of the rib channels would be the thinest material and the center of the unsupported tank would have the maximum flex. I would think cracking at this location would be a common problem.

I've read to drill out the ends of the crack. I'm not sure I can find the end of the crack since it's so hard to see. I've read to use Water Weld 2 part epoxy putty and maybe seal the putty with something else to keep it from seeping.

I've read that the tank is made of ABS plastic and could be patched using ABS cement to bond an ABS patch to the tank. I don't know if there is such a think as an ABS patch that could fit inside the rib recess.

My thinking is to drill a series of holes where I think the crack is and stuff in the epoxy putty using the holes to help anchor it but I'm nervous about causing more tank damage.

What is the preferred way to fix this type of crack? Putty or ABS patch?

Should we be thinking about providing some structural support for the bottom center of the tank so that it doesn't flex up and down to generate more cracks?

-Jeff