I have a new colnago mix that I got for really cheap on eBay. I like the geometery a lot except I would like the head tube to be a bit shorter-- it sticks up about 1.5cm above the top of the top tube. What is the best way to cut this off. I brought it to my LBS and asked if they would just use the facing tool to cut it down to the point I wanted (about 1cm) and they wouldn't do it. They said the Al frame is too soft and could deform causing problems with my headset fitting and overall longevity of the frame. Any suggestions?