Be careful. Flowers are a lot like tigers and intimitate easy and dont feed super aggressive. Just divided them for a few weeks and get it feeding very well and fat. Onces everything is good, you can let them go together. Hope that helps some
To me , its a case by case situation. I would mix them up and have a plan b should the other "aggressive" rays act like it. I have a 11 marbled motoro very "aggressive" with a 8-9 inch tiger (a timid ray supposedly ) and they play along fine..
It should be fine, colombian schroederi are not has fragile as some might have you believe. They can be tricky to acclimatise when first imported but once they are settled & feeding well they are as tough as any other ray.
I keep mine with leos & henlei & they get along great, if anything its the flower that has the upper hand