Focbox unity antispark switch

Hallo! I am building an 4wd direct drive esk8 !
2 untiys. But i would like 1 switch to turn both on or off… Since i already have a few roll to start antispark switches from Martin sp… Can i put "external ’ antispark switch to it and put it on and off with thát switch? Without using either of the switches build in the untiys…? Any other advices reagarding to wiring and or programmering the untiys.

Thnx!

Sam hoekstra