Can't be done alas. The TO p336 construction state "Capacitors can only modify one PPC and do not stack."
I would point out (barring errata that I haven't checked..still), that the rules only really say that capacitors can't modify more than one PPC and that they don't stack. "Don't stack," is rather nebulous and I read it as "you can't put 4 capacitors on something, and get +20 to damage," but it doesn't specifically state "You can't put more than one Capacitor on something,"
if they did intend to only allow for a single capacitor, no clue why they wouldn't have simply written, "Capacitors can only modify one PPC, and a PPC can only mount one Capacitor."
There are limited uses for multiple Capacitors, namely storing up energy over several turns, and then firing for several turns, and if you take a critical hit on the same turn as firing, you would only burn out the Capacitor, and not the entire PPC, so there is some redundancy.
Mind you, I'm guessing the answer is going to be "One Capacitor per PPC," but I did find it interesting that the rules don't actually say that.