Hi Fabieville,
I know those EPEver Tracers well... Sold and installed them by the hundreds! For the money they are excellent charge controllers.
As with all MPPT charge controllers, it actively controls the output current by moving the power-point to either get maximum output from the panels, or limit its current to 40A by moving the power-point for the panels at a higher Voltage then where the maximum would occur. The limit is baked into the firmware, and while there is a current sensing device somewhere (probably small resistor) that you could fool, as others noted it won't end well. While better than average for product from that country, it's still Chinese, and I'm sure they are walking the fine line between meeting specs while cutting every corner they can.
As with any MPPT charge controller you are free to oversize the solar array with respect to that maximum output current. We've had people put 150% of rated on these, all that does is cause the output to clip at 40A if there's enough sun. On the cloudy and winter days you get the benefit of the extra solar Watts though! The specs and manual just list how much solar will result in maximum output under certain conditions, it is not the limit of the charge controller. Also keep in mind that a 24V battery bank charges closer to 28V most of the time, and solar panels rarely produce rated output, so 40A x 28V = 1120 Watt; with your 1280 Watt that's only a 114% oversize, it wouldn't clip very often!
Now, having said that, there is a limit to oversizing the array before things "get interesting" (as in, 'the magic smoke comes out'). There comes a point where the processor just isn't fast enough to move the power-point of the controller to limit the current to less than self-destruct values (when a cloud moves away from the sun, and output spikes very quickly for example). The more expensive charge controllers (Morningstar, Outback, MidNite) are made there you can pretty much throw anything on the input, but EP-Solar/EPEver isn't quite in that class. I'd limit things to about 150% for this one to be on the safe side.
-RoB-