AFAIK there is no way for OpenRocket to model the Cosmic Interceptor's rudder/wing configuration -- there may be some hacks to get it to look right, but it won't be properly reflected in the sim. The best you could do is model it with an asymmetric four-fin configuration all centered on the BT.
I've never bothered with OR for mine. I've found that putting the weight in correctly and entering the Cd as 0.9 in thrustcurve gets me pretty close. I've flown mine on E20-4 and F35-6 and one flight on an E12-4, which I would only repeat with low wind and a long launch rod.