My guess is that you want to have a harness that you can plug in when you use the 4s pack and then remove it when you want to run two packs. If this is correct you just need a plug for the open pattery plug in your SV. This plug would have a wire that goes drectly from your positive to you negative on the open terminal. (just short across them to complete the circuit). You can just buy male deans connector at the LHS and solder a wire between connectors. When you use your 4S pack you plug it into one plug (I'd recomend the starbird side) and just plug the conector into the other plug. Now the only problem that you need to address is the weight balance issue. In the future I'd stick with 2, 2S packs for this reason. (but I'm sure the price was right)