Atmos handling

I have been using my system as stereo with sub woofer for my stereo mixes from my DAW. My main outs and the center, side and rear outs are through the sub. System is 7.1.4 so I have direct connects to the 4 top speakers as sub only provides 5.1. Now I am attempting to set up Atmos playback from my DAW and wondering how to cope with bass management? Since the sub is an integral part of my stereo setup, I don’t know how to route for Atmos. Right now - in an atmos trial, panning to my left front and right front speakers, it sounds like they are missing the sub, but panned to the center the sub is there… Any recommendations on the best way to set up the 7.1.4 without having to re-wire?