Thanks for pointing out the example on pg.171 - I had completely missed that

So that clears up the ranged weapons, but not the melee ones.
Nothing in the section on Touch-only attacks on pg.187 says that the damage is flat. Neither the damage section on pg.169 or the descriptions of the melee weapons on pg.421-423 mention anything like that either.
Under Grazing Hit on pg.173, it says that on a tie you make contact, thus allowing certain attack types to do damage - shock gloves are specified here as an example.
So the way I'm reading the rules now, stun weapons work like this:
Ranged weapons: just like any other ranged weapon, add net hits to damage
Melee weapons: just like any other melee weapon, add net hits to damage - additionally on a tie you win the opposed test because you made contact and can do the weapon's base damage
Grenades: Just like any other grenade weapon, damage is base damage value only
Is that correct?
R.