Jim here has been known to routinely exceed panels specs, up there in the mountains :)
Yes, 60A MPPT would handle 900W and even 1000W flat array at sea level, hardly ever hitting 60A. At 100 Vmp input the controller efficiency will be only 90%. Also, the panel itself will drop the output in the heat of summer. OTH, in winter a flat panel will be getting 1.5-1.7 times less sun radiation, so there is nothing to worry about.
Make sure you connect voltage sense wires. Post-controller V-drop at this power will be horrendous.