Originally Posted by
chucky
It will be fine, just make sure you tension the headset well: Sheldon Brown says you can tension it just with your body weight, but I find a string tied to the stem and the fork works much better.
http://www.sheldonbrown.com/handsup.html
To the naysayers: smarter more experienced people than you have recommended worse.
Uhhh no, if you really read what Sheldon wrote and what the OP first proposed you would realize the two are not at all the same. Sheldon was discussing leaving a
threadless steerer extra long and using the extra length to allow the handlebars to be placed higher. He did not say anything about splicing an extra length of steerer onto the too short one and using it to fit a threadless headset.