Hi Radical Departure
I designed and built a SPAD pusher/puller using two standard .28 Magnum engines and 9 X 6 props. The rear was a pusher prop. My plane could not do a crisp snap roll. Since I do snap rolls with all of my planes, I decided that the reason was the props going in opposite directions. As I recall, it could also not do a good Hammerhead stall. What Red B is suggesting may be the way to go. Since it is electric you can experiment with both. Let us know.