My early 60's Ideor road bike has a steel Ambrosio stem. It has no minimum insertion line. I'm trying to get my handlebars up a little because the frame is just a tad too small. Any ideas how much of the stem I need to have inserted to be safe? Since it's steel, can I have more of the stem exposed than on an alloy stem? I'd like to keep the original stem and not change over to a Nitto Technomic. Thanks.