http://www.palmbeachbiketours.com/su...r-second-stem/ Here is another solution to your problem if........you don't have a cut to length steering tube.
On my bike I found that I could attach a second stem to my primary stem because the neck of my stem is the same dia. as my handlebars. Then I bought a piece of 1-1/8" dia. aluminum tube and put it where the second stem would attach to the steering tube and it works perfectly. It holds my bag, computer, lights and mirror. I have pictures on a thread "I Need more Room" (sorry i don't have the same pic's on my work computer)
Anyway, that might be a solution as well.