I prefer to have 'B' as R1 and 'C' as R2 which leaves 'A' as square and 'D' as 'x'. It feels a lot easier and I can actually get combos out with this setup.
Carl is so fun to play with. Are you just randomly throwing the robot out? I usually just do 5B>6B>623C(robot-toss)>5B and if Ada is near by, add 623D after robot.