I would guess that you have a 52 on the front and a 13 on the back. You should be able to move along pretty well with this combo! Like I said, equallizing the effort is the hardest thing. In my experience, if you're not carefull, the stronger rider will take over and make it too easy for the weaker. When we drifted away from the tandem about ten years ago, my wife was not riding her single and was not keeping up her skills. She was working less and I was killing myself. A couple of years ago, she started riding single again and got into really good shape-she was riding during the week and was probably in the best shape of her life. When we started to tandem again, she was full of piss and vineger and sometimes I would have to tame her down on the hills; besides her possibly burning out, it was causing me to answer with more energy than I could spare. If your wife wants a workout, find some hills! Seriously though, hills can be tough on any tandem and too much climbing can turn off a stoker quicker than anything! Do you have a speedo on the tandem? This would help. You will be amazed how much faster you will be on the tandem than on your singles. When you are not maintaineng a consistent reasonable speed or riding with a group, sometimes the speed spirals out of control in a sub-conscious dual between partners!
Also, again, be patient...the balance stuff will get better with a little experience. I still like the idea of a v-brake on the front. To do this with your levers, you will need a "travel agent" equalizer.