I also ride a tandem, but an MTB one (talk about scared sometimes ). On our tandem the other half always goes in front for two reasons - 1) the size thing, the front of our tandem is too big for me to control confortably and 2) the weight thing - the SO is about 4 stone heavier than me (about 56 pounds if my maths is correct) which also makes it more difficult for me to control the bike. I have watched the SO ride on the back of the tandem with a male friend who was similar height but much lighter and he found it very difficult to control as the SOs weight had a big influence on the movement of the tandem.

In general I enjoy it as it gives a much harder workout than the solos on some of our local offroad stuff however I still prefer riding my own bike due to control, I like the feeling of picking a line etc offroad, as a stoker you are reduced to being an engine only which can get tedious quickly. Although for kids on the back it does have the advantage that you can actually look around at the scenery rather than look where you are going.