[CR] Installing stem on handlebar without buggering the bar?

Team CR:

I am trying to install a used Cinelli 1A oval logo stem on a new bar - an "Ambrosio 13 Volte Champione del Mondo." The Velobase picture of the bar is here: http://www.velobase.com/ViewSingleComponent.aspx?ID=9DCB7458-1042-46ED-B570-EAC15E104876&Enum=112&AbsPos=0

I can get the stem up to the start of the wider part in the middle of the bar, but it is clear to me that I am going to bugger up the bar if I keep pressing the stem toward the middle, where it has to go. I have put a wooden wedge into the opening on the stem (the kind you use to straighten up a door frame), and this has given me bit bigger opening, but it will not be enough.

What am I not doing here that should be obvious to me. I really don't want to mar the bar, as I will lose sleep. Should I use a hardwood wedge? Should I bathe the bar in liquid nitrogen and heat the stem? I actually searched the archives and found nothing, so I fear I am missing something really basic. But there are not many variables left.

Thanks.

Bill Kloos Eugene, Oregon "Last refuge of the terminally hip."