There is no reason to disable the second element. If you're using 11,000 watts, I would rather PWM at 50% running both elements than to leave one elements on at 100%. People are rightly concerned about maintaining the lowest watt density they can get away with and that's exactly how you'd achieve it.
Two ways to get there. Use a single 60amp SSR and break it down to two outlets afterward. Break your 50amp feed down to two 10 gauge wires and run them through 25 or 40amp SSRs, both triggered by the same PID (or EZboil which I much prefer).