I would not trust them together long term. The problem I had was one of my rays kept trying to pounce on my weeksii. They were both 8 inch. The weeksii turned and bit the ray pretty hard one day. The other problem I had with my endlicheri who was 10 inches was he would push himself under the rays to try and steal the food they were eating. So it will be a trial and error thing. What works today might not work tomorrow especially as the fish grow and their personalities change.
Thanks for the replys people. I am going to or still plan on putting my motoro with 6-9 senegals, 2 ornates, retro, endli, and any other species that i happen to find when fish hunting.
I tried senagels around 9" with my rays when i first bought my rays and he went straight for my rays eye's, i removed the senagels, so beware, might work but might be bad.