Contrary to the replies on this question, I am the stoker and in our numerous falls- I come off best. Perhaps it is years of falling off the solo, but I have either rolled away cleanly, or I have managed to roll up on the Tandem with the fallen side pedal high so that I am not in contact with the track, and the stokers bars keep my body away aswell. I never put out a foot or arm to ease the fall, but they happen so quickly, that there is never time to do this in any case. My pilot is the one taking the brunt of the falls and on one memorable fall last year at high speed on a rough downhill, he finished up cuddling me round the neck to protect me. How that happened neither of us know, but torn hand ligament through trying to keep the bar straight and aches all over the body for a week after. I was fine.
Then on the few occasions I have piloted and had a fall- I have definitely come off worse with clothing being damaged and once a pulled calf muscle- 20 miles from home that did not allow me back on the bike for a further 3 weeks.

I must admit that practice must make perfect as we generally fall off on most rides at some point but I also do that on the solo too.