The Canon 1DX MKII would be better suited for the M10 & M15. The MoVI M15 has a weight limit of 15 lb (6.8 kg) The MoVI M10 has a weight limit of 12 Lb (5.4 kg), the MoVI M5 has a weight limit of 5 Lb (2.2 kg). Factor in the weight of your camera/lens combination and if you decide to add additional equipment. Anything mounted on the top cross bar does not affect the weight limit on the gimbal. **Size and shape of your camera package is also a factor, not just weight.** Please see the attached camera chart.
I have 1DC and and 1DX Mark II has similar size as 1DC. I am not comfortable using 1DC on M5 but it's doable. Since this is a wide camera, you need a clearance on the HDMI port to plug in your cable. The only way to balance the roll on M5 is doing it from the camera tray rail and it will not give you enough clearence for HDMI port. As a solution, I put some weight inside one of arms so I could push the camera all the way other side to have HDMI clearance and have balance. Once you do it, you will have good results. And you will need longer vertical tilt tubes (15mm) to top mount the camera as well which I would suggest you to do. Hope this helps.