Wonder whether on that kind of terrain you might be better off with dual hub drives —
That’s what Grin Technologies recommends for heavy loads up hills: Dual Hub Motors
“Dual front/rear hub motors on a bike is an excellent way to achieve higher power levels than a single hub motor can produce, and is especially useful in cargo bike or load hauling applications. When you run two brushless motor systems on the bike, each motor requires it's own motor controller (there is no way around this) but the throttle signal would typically be split to run both motors equally. For controllers running with our new WP8 Cycle Analyst plug, we have a very convenient
dual controller splitter cable. For older controllers with the 6-pin CA plug, or generic controllers with no CA plug, you can run two motors with a V3 CA3-DPS device using the
dual motor CA shunt, while for those without a CA we have a simpler
dual controller throttle splitter cable for the same purpose.
“Most often you would use matching motors for the front and rear, ex dual eZee motors, dual Crystalyte, dual 9C, and the power would always be split 50:50 between the two motors. However, there are cases where running different motors makes sense too. A popular one would be a rear eZee motor and a front direct drive like the Grin All Axle. The eZee motor would do much of the grunt of the work on steep hill climbs and the likes, while the direct drive motor provides regenerative braking and runs at good efficiency when riding on the flats.”
I’m using just a pair of Bafang 500W hub motors and 52V Luna DireWolf packs on my e-cumbent cargo bike and can easily conquer the steepest grades in the Hudson Valley on the 39T ring and 28T cog when the bike is fully loaded. Am not generally off-roading though until I come home and have to ascend my loose pack gravel driveway then make it around the grassy knoll upon which my house is perched to get to my own apartment’s entrance on the second floor. Would skid out on just a single hub drive.
Hope the new installation works out well for you TRIBUNAL.