I had string problems so I searched for info on this UU Forum. FYI I have written down today's exercise. I have two Tenor Ukes.One of which I wanted to change one Tenor to a LOW G string configuration. Tried Fremont low G, and the Fremont low G was too over powering (Booming), took the Fremonts off and replaced with Aquila Tenor strings. Recently bought Worth Low G (colour dark), started to fit them and found the Worth Low G string sounded fine,......BUT, the low G string buzzed on five fret positions. I shimmed the nut (raised it) with a slim sliver of brass shimstock, BUZZ still there. Tried another slightly higher bridge insert in the slot....it still buzzes. It is frustrating, because I can clearly observe the increased spacing between the nut and the fretboard. The credit card trick, hardly holds, due to gravitional pull. This little exercise took me well over 3 hours, and my conclusion is that the Worth low G string must be too floppy, or the peak value of the string (as it oscilates), is so high, that it touches somewhere on the fret board . I removed the brass shim, brought the bridge back to its initial position, refitted the Aquilla (High G)Tenor Strings, and the Buzz is not there anymore. The search continues.....