When you intonate with a floating bridge, proper intonation may require the bridge to be at an angle. It all depends on if your uke tunes up and stays in tune up and down the neck. Check the 1st string's 12th fret harmonic with that string's note on the fretted 12th fret. If the fretted note is sharp, move the bridge closer to the tailpiece. If it's flat, move it closer to the neck. Then do the same with the 4th string and pivot the bridge on that side where it intones properly. You may have a bridge on an angle, or it may be straight. Some people will intone the 3rd string and put the bridge in an average spot between where it intones on the 4th and 3rd string, leaving both a slight bit out of tune, but close enough. Use an electronic tuner. When you change strings, you will have to start over, especially if you change brands. A pencil mark is a great idea to keep you in the ballpark.