Try a better adapter that absolutely will not slip.

Velo Orange stem adapter - silver http://www.velo-orange.com/vothstad.html
Dimension stem adapter - black http://www.treefortbikes.com/product...22361381___314

Or get a nice Nitto knurled surface one for $60. !!!! Absolutely the best quality. http://www.benscycle.net/index.php?m...43ebfafbbc3e04

Or, get some 1-1/8" shims to put under the stem..... lowest cost solution.