according to the enlish translated 190a8 technical manual i have, the weapons selection is electric and has only 2 switches, switch 1 is inboard (cowl and inboard cannons) and switch 2 is outboard (outer wing cannons), the mk103, gondola mounted mk108, and gondola mounted dual 20mm cannons are outboard weapons. if you would like a copy of the full pdf to read, pm me.