You use the rear brake then?
Why wouldn't he?? Over the years, I've heard lots of "sports" riders telling newbies to forget the rear brake altogether -
never use it - and it just makes me laugh. Why the foc would you not use the rear brake? In urban riding I use my rear brake
all the time to come to a steady, slow stop (eg approaching amber/red traffic lights, etc). It gives you the right amount of reduction in speed and doesn't have the bike diving.
If I need to stop much quicker, I always start (momentarily) with the rear brake followed almost immediately with the front. The front brake is obviously the most powerful, providing the vast majority of braking force, but in an emergency stop, why the hell would you leave out some braking effect? True, it's easy to lock up the back wheel, but when you use it all the time in your riding, you get to know it and understand when enough pressure on that pedal is enough.
CliffRose : I wouldn't bother fitting a rear caliper designed for a much bigger bike - just focus on getting to know the one you've got. It's only there to provide a fairly small proportion of your braking - don't make it easy to lock up the back wheel.