Okay, I've been giving this some thought (from both perspectives), and came up with this:
If you want to hit someone with both P and S in a smack, you first roll your unarmed combat + agi to hit him as a normal punch. Say that I have 12 dice in that pool, that gives me 4 net hits statistically. However, my opponent rolls reaction + dodge (say 4+4), ends up with (counted high) 3 hits. Counting backwards, I get 1 net hit. All good so far, he gets (str/2)P+1 damage to soak.
Now, I want to deliver the shock from my shock hands. Taking into account that I can normally deliver 6S(e), I set a threshold at 6 (this is to signify how hard it is to deliver that kind of shock; a smaller charge does not have as much damaging potential, and so a lower threshold for balancing purposes). Every net hit from my above strike counts down that threshold (to signify how well of a contact surface my hit actually created related to the difficulty of the shock itself). I roll the normal damage plus any net hits above as my dice pool (6+1), threshold 5 (6-1 for my one net hit above) and come up with ~2 hits, not enough to beat the threshold. No S(e) damage get through, coz I didn't hit well enough. I struck him, yes, but the resistance in the hit area was too great for the shock to be delivered.
If I had 6 net hits in the first roll, the threshold of the shock would be a normal 1, but since I still roll the shock-strike, I have the potential to get no hits, glitches or critical glitches. 6+6 gives you 4 hits statistically, and that's 6S(e)+3 you deliver as well as the (str/2)+6P.
Also, by no means should the net hits of the shock-roll be higher than the first hit; I can't deliver a bigger shock than my contact surface (the resistance of it) allows.
This way, you will need a major hit to be able to both do physical and stun damage in one hit, and also, you cannot shock your victim to a greater extent than you actually hit him. If you want to shock him properly (without risking killing him in the process), touch attack him instead.
Note:
It's about 5:30 AM here, so my logic may be flawed.
But still, what about the concept?