I would recommend copper-wire or normal wire

I will be doing this mod to myself, i am waiting on 2 more scuds, i really like the non intrusive way that 'cantruchd' did, i will of course be using wire of some sort, everything should be fine with this mod and the really good thing is you can peal off the tape and make 2 single battery's if you wanted, but thrust me when you first get a dual setup and get the very long battery time/life you don't want to go back, and again the mugen cover helps on typing etc...

It actually feels awkward when it is 'thin'