All this talk about slipping Cinelli bars got me thinking about the British
solution to this problem.
Old GB bars, such as their Maes and Dayton models, had a shim between the
bar and the handlebar clamp.
The purpose of the shim was not to strengthen the bar ... but simply to
enable the drop bars to slip into place.
Once in place, the weight of the rider going over bumps would easily deform
the outer ends of the shims.
See http://www.flickr.com/
To enable the clamp to get a good grip on the bar inside the shim, the shim was split or opened in some way. If the shim was a tube, that was not press fit, or had loosened with use, then the clamp would have to deform the shim in order to grip the bar inside. That would take a lot of force.
Not having seen photos of the bar, I would have to agree the slitting the Cinelli bar's shim was the best option, but only if could be done without damaging the bar.
Amir Avitzur
Ramat-Gan, Israel