The best bet is to use a flybarless gyro with a built-in on/off switch.
The MSH HD gyros (iKON 2 HD / Brain 2 HD) have built-in heavy duty battery lead and a fail-on pin switch for remote on/off
You can also check out the on/off switches from Perfect Regulators or Castle Creations
Most HV heli setups in a 600 / 700 (or larger) flight system will draw 20A peak if they are flying hard 3D / smack style.
Powering on and off the flight system would see a low current. That would be 100mA to 300mA as the gyro initialized and started sending signals to the servos.
The diagram in the previous post would be good for super high current applications like a motor arming switch mainly because it looks like it is using a Deans-style plug / connector
It is kind of overkill for a receiver / fbl flight battery.
But, it would work
Most 2S LiPo battery leads use 2 "servo" style leads to connect to the FBL. This is typically a Y-cable with the Deans-style connector on the LiPo and the 2 servo-style connectors on the FBL.
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