Does anyone know if it is possible to use both the Speedlite radio transmitter and the Speedlite optical transmitter at the same time with one camera by using a PC terminal and an extra shoe or something like that? I have a 5DMkIII and an optical transmitter with several flashes. Considering purchasing the new radio Speedlites. Any idea if both transmitters could somehow be connected to a camera at the same time and if they would work together so that you could mix radio and optical slave flashes without having to use the 600EX-RT as optical?