>>46980412I did it with 6ex Gloria and no 6ex Steven. Basically what I did was change my normal grid to this
https://ng-pomatools.web.app/pairs/24300/88801?s=5&l=135&r=5&p=0&a=0&g=AAECAwQFBgkRFBcYGxwdICMoLi8 and make use of Laser-Sharp Focus to sync accel and get in 2 syncs by the time limit. Only difference for you is that you'd be syncing with Steven and not Gloria, which might be easier as he has Haymaker, Quick Moves and [assuming 3/5] a higher Flinch Chance.
here's a video of an EX Steven Clear that I found [not mine][ which might help
https://www.youtube.com/watch?v=4aPU-MbuYGobasically you just want to rush sync and make use of the sure-crit moves on the mon that isn't syncing. i actually fucked up my quad queue and didn't realize my Steven didn't actually have CS2 until after the fight so there's some room for error. Also Jasmine seems to need the 2/5 for Clang Lockstep, 3/5 and higher probably help too because of stuff like Berserk Bunch.