NAA learned about slats from the F-86. PRobably whatever is on the F-100 is very close to what is on the Sabre.

For LE flaps, the hinge moments could be high, which means the servo loads could end up being high, even when at 0 deg. That idea about the over center arm is a good one. That flap will always be trying to deflect up, even past 0, especially at high AOA. Be aware of that, watch your Rx battery power consumption etc.

LE flaps will allow you to go to higher AOA before stall, similar to a slat but not as good. At low AOA they won't make a difference in lift - they really just extend the lift curve.

They are useful for landing approach, getting that nose up to create drag. You could also mix them with elevator and TE flaps for high g turns, not unlike the control line stunt models of old.