Wide and narrow stance in bumps is a relative term. If you are not good in bumps now, my suggestion would be to ski them in the stance width that you would normally ski short turns on groomed with.
Good in bumps is also a relative term. Everyone has their own ideas. Good generally falls into two catagories. Those bump skiers who can rip the zipperline without need for speed control and those bump skiers who look like they are on a Sunday stroll, silky smooth and in perfect balance.
Skiing bumps in a narrow stance (feet very close together) makes for ease of pivoting skis and easier absorbtion of impact. Narrow also makes you rotate faster in the air for freestyle points. If your idea of bump skiing is zipperline, high speed, in the air spinning much of the time then by all means consider a fairly narrow stance.
For the bump skier who wants a comfortable ride with good speed control, a narrow stance restricts the amount of edging and therefore, speed and line control, that you can achieve. A wider stance, say 6" between your feet, allows you to guide the skis better and develop some angles for edging. All of this leads to better control of your line and speed, greatly reducing the need for absorbtion and dependence on the bumps for rhythm. With greater selection of line, you won't get thrown after 4 or 5 bumps. For all but the young and very athletic, this is your only good option.
Hope this helps.
[ July 01, 2003, 04:11 AM: Message edited by: Pierre ]