Cover the top of the weir somehow, use egg crate or something so the ray can not actually get into the overflow. I have lost a new born over the top of the weir combs before but luckily managed to retrieve the pup. Since then I have made the weir combs taller so nothing can actually get over the top.
Welcome to MFK! Make a make shift net or use lighting diffuser. I did this but my rays don't try to swim that high but my smaller cichlids when they get spooked get into the overflow. Usually they get into the net and jump back into the tank but one guy ended up drying out and dying in the net. Even if a ray were to get on top it has "feet" so they will be able to get around it and get back into the net.