You could try it, but it might be risky at this point.
I have 7 clowns ranging from 2 1/2"- 5" w/ my two 8" oscars and have no problems.
When I got the oscars as juvies, I also started with three clowns.
So they were rasied with clowns. I also never fed live feeders so they wouldn't be tempted.
The last time I added additional clowns to the tank, the smallest was just under 2". I was alittle nervous when I first added him,
I figured he would run for cover. Nope, he headed right for the oscars and swam right in front of their faces. The oscars just ignored it. I haven't lost one clown and the tank is over a year old.
I think it makes a big difference in how you feed it and if its raised with other tankmates when small.
Exmple:
My daughter had a 8" oscar and she fed it feeders now and then. She had tank problems so I let her move the oscar into one of my tanks for the time being.
At the time my tank only had two 3" bullheads in it. I didn't think nothing of it, until I found them missing!!
Clowns can be expensive snacks. So if you want to try it, try to find the biggest clowns possible. Have lots of hiding places.
Clowns are also prone to ick so be sure to quarantine for a few weeks before adding to the main tank.
They also get big but grow slow.
Out of curiousity, what size tank do you have?