Originally Posted by
FBinNY
The key in braking isn't the pads but the "swept area" on the rotor, and it's ability to absorb and/or radiate heat to the surrounding air.
This would imply fitting the largest diameter rotor possible, on both front and rear. Also suggest a two-piston caliper design, which may self-adjust better than the single-piston plus fixed-pad variety. What have you got now?
Something like the Kool-Stop "Sintered brake compound with copper plated back plate" or "Electric bike compound" pads at
Kool Stop International - High Performance Bicycle Brake Pads Since 1977 may handle the heat better than organic or semi-metallic pads.