We ended up taking the both of them out together for the first time. We figured Kiba was doing well enough and it was going to end up happening eventually. They actually ended up behaving fairly well. Especially since we were worried about them being in the car together. But, Tsume just stayed on his side and Kiba stayed on his. Though Kiba doesn't tend to move from his window as long as we have it open for him. So, hopefully we can do this a lot more now. Just don't think I'd be able to handle them both on my own either way. Tsume needs a lot more leash training and would probably rip my arms off trying to control him and Kiba.