Probably the slowest here. I clocked over 50 kph on a slight downhill. Of course the speed I could do depends on the size of the hill. If I found a large hill without a lot of bends on the way down, I could go as fast as anyone else. But if I came off, life may cease to be fun.
The real question is how fast do you go when you are on a flat road? Again I am slower than many here. When I am just taking it easy, and not in a hurry, I used to cruise at around 15 kph. However, I have lost some fat, and gained some fitness. I now cruise at around 20 kph when I am just taking it easy, and not in a hurry. I am strong enough to go fast, but only for a short time. I am not as fit as some.
To all the other fat challenged people out there. Don't worry if you are not as fast as others. Just work on getting fitter.