Any low G will likely require opening up the slots in the saddle and bridge. The Fremont fluorocarbons are slightly smaller in gauge then nylon but the low G is still larger than the high G nylon. If you have a thin file a V groove can be filed into the nut slot or it can be opened up with a piece of folded sandpaper. It will take some time and you might want to mask the wood above the nut to avoid scratches. The goal is for the string to rest fully on the zero fret with the slot in the nut just big enough to guide the string and hold it in place. The string should pass thru the nut freely. If you have the opposite problem with the slot too wide causing the string to click back and forth while playing, you can pad the slot with a piece of tape or slip a small plastic sleeve from a piece of wire over the the end and in the slot to take up the room. Similar to the sleeves used on violin strings to protect the bridge. The slot in the bridge on the uke may also need to be opened up which will require sanding wider with a folded piece of sandpaper. Again its best to mask the wood around the bridge to avoid scratches. The string can be snug in the slot but should seat fully to the bottom of the slot.